September 15, 1997
Dr. Nicholas F. Fiore
Carpenter Technology Corporation
October 20, 1997
Dr. Karthik Ramani
School of Mechanical Engineering, CPPL Lab
Purdue University
Topic: Polymer Bonded Systems: Materials
Processing and Mechanics
December 15, 1997
George F. Vander Voort
Buehler Ltd.
Topic: Three Mile Island Nuclear Failure
January 26, 1998
Niel Merrell
Contour Hardening Inc.
Topic: ADVANCEMENTS IN INDUCTION GEAR
HEAT TREATMENT
March 16, 1998
Speaker - Students of Metallurgy (Purdue)
Topics: Texture and Anisotropy in Piezoelectric Ceramics
White Iron Flaking of Rolls Utilized in the Soybean Processing Industry
April 20, 1998
Dr. B. Keith Moore
School of Dentistry - Indiana University
Topic: MATERIALS BEHIND YOUR SMILE
May 19, 1998
Dr. M. R. Louthan, Jr.
Savannah River Technical Center
Topic: WHY STUFF FALLS APART
September 21, 1998 Joint Meeting with ASME
Speaker: Mitchell Spencer from Magnequench Corp. of Anderson, IN
Topic: High density magnet technology and applications
October 19, 1998 Chapter visit by Dr. Alton Romig, Jr. (President ASM)
Dr. Alton Romig, Jr.
Sandia National Laboratories
Topic: Micromachines: An Enabling Technology for the Future
November 16, 1998 Heat Treater's Night
Sandy Cioletti
Heat Treaters Network
Topic: Options for Training Employees for Better Heat Treatment
December 14, 1998 Fred McMann
Carpenter Specialty Alloys
Topic: Precipitation Hardened Stainless Steels -- New Alloys and Applications
January 18, 1999 Sustaining Members Night
Patrick Foster
LECO Corporation
Topic: What's New in Metallography?
March 15, 1999 Joint Meeting with Lafayette/Kokomo(Purdue) Chapter
Scholarship Night
Speakers - Aaron M Scroggin & Marc Yap (Purdue)
Topics: Development of Pressure Sensitive Paint
Topics: Powder Metallurgy for Spinal Implants
April 19, 1999 Awards Night / Past Chairmens' Night
Annual Business Meeting
Denesh Seksaria
ALCOA Automotive Structures
Topic: Present and Future Roles of Aluminum Products in Transportation
September 20, 1999 Joint Meeting with ASME
Speaker: Rodger Seeley, Haynes International
Topic: High Temperature Alloys
November 15, 1999 Heat Treater's Night
Allen Golden
Surface Combustion Inc.
Topic: Endothermic Atmosphere Chemistry and Control
December 13, 1999 Sustaining Member's Night
Paul Crook
Haynes International
Topic: Ni-base Corrosion Resistant Alloys
January 24, 2000 Financial Seminar
David Gilreath
Morgan, Stanley Dean Witter
Social Night - Show Boat @ Beef & Boards
Buffet Dinner and Jerome Kern Musical
March 20, 2000 Student Night/Scholarship Night
Michael R. Brickey
Topic:Structural and Chemical Analyses of a Thermally Grown Oxide Scale in Thermal Barrier Coatings Containing a Platinum-Nickel-Aluminide Bondcoat
Thomas R. Kanaby
Topic:Evaluation of Milling Cutter Weld Processing Failures and Other Selected Projects from TAP
April 17, 2000 Annual Business Meeting / Past Chairmens' Night
Alexander H. King - ASM Fellow - Purdue University
Topic: Little Things and Big Pictures: ongoing research and new materials research projects at Purdue
May 15, 2000 Speaker: Dr. Glenn Whichard
Topic: Thermal Spray
Why Stuff Falls ApartDr. McIntyre R. Louthan, Jr
Savannah River Technology Center -- Westinghouse Savannah River Co.
Dr. Louthan presented both humorous and touching illustrations about how catastrophic failures can be traced to six root causes.
1. Deficiencies in Design.
The collapse of the skybridge at the KC Hyatt was a prime example. Loadbearing hangers were split, concentrating loads above the coupling rather than distributing them as originally conceived, because 60 foot rods were "hard to handle".
2. Improper Materials Selection
An averted crisis involving the cancellation of a shipment of crane arms made from high ductile-to-brittle transition temperature steel to be shipped to the arctic was an example.
3. Defects in Material
A steering gear casing which passed a 1% AQL, but in which the lot was known to have some casting defects leading to a tragic driving plunge to death for a family was an example. Non-destructive inspection was withheld due to cost.
4. Improper Processing
A supplier supplied rolled (rather than forged) roof bolt plates for a mining application to save money. A worker was killed when the first collapse occurred.
5. Inappropriate Assembly
A major problem was averted when the manufacturer of large compressors discovered that a plater of head bolts had failed to bake out the bolts after electroplating leaving them susceptible to hydrogen embrittlement. Immediate replacement of all bolts in the field prevented a disaster.
6. Inadequate Service
Our speaker's oldest son (a graduate engineer) froze up his new van's engine when he didn't check the oil for over 13000 miles.
The be a true "professional"
Engineers need
Tough Preparation
and
Flawless Ethics
Our universities are sadly deficient in providing the second component.
Materials Behind Your SmileDr. B. Keith Moore
Indiana University School of Dentistry
Dr. Moore gave an interesting look at the materials used in restorative dentistry, how the are selected and fabricated. Some FAQ's (frequently asked questions). Are these materials safe? Why do they cost so much? How long will that filling last? Hasn't fluoride in water and toothpaste eliminated the need for dentists? Unfortunately, we did take a good set of notes on this presentation, from which to do a write up.
Presentations by Purdue Materials Students -- William F. Shelley Jr. & Erica D. Cattanach
Presentation #1: Texture and Anisotropy in Piezoelectric Ceramics
William F. Shelley Jr.
The properties of piezoelectric ceramics, namely lead zirconate titanate (PZT), are widely known, however, the relationship between the properties and the texture of the ceramic are not well known. The present research studies the degree of texture in Navy II PZT (Channel Industries) and the mechanisms of introducing texture into piezoelectric ceramics. X-ray diffraction was used to qualitatively observe texture in Navy II PZT, and fracture toughness was studied through Vickers indentation and four-point bend tests. Fabrication of oriented green bodies is also being studied in hope of tailoring the electrical and mechanical properties of piezoelectric ceramics through powder processing techniques.
Presently the technique of centrifugal casting is being applied to attempt to achieve layered ceramics with varying amounts of lead titanate at the one extreme, to lead zirconate at the other, with intermediate layers in the realm of common PZT compositions. The advantage of such a layered structure is more strain available upon excitation of the piezoelectric. Difficulties have been to get good suspensions of the ceramics in order to cast the layers. Both electrostatic control and steric control have been employed to try to achieve such suspensions. Initial results of the layered ceramics failed to sinter through, leaving a soft core. More work is planned to overcome this and other problems.
Presentation #2: White Iron Flaking Rolls Utilized in the Soybean Processing Industry
Erica D. Cattanach
In order to extract oil from soybeans, soybeans are flaked to about 0.010 inches thickness between two rolls sping at about 300 rpm. Flaking rolls are made of white cast iron primarily for wear resistance and low cost. The wear and degradation of these rolls are the primary focus of this study.
A new series of white iron containing small amounts of niobium are under development for this application. Experiments are currently underway at Central Soya, Inc. Morristown, IN plant to directly measure wear resistance. This is the first systematic study which applies scientific principals toward understanding the industrial difficulties involved in flaking soybeans.
Primary emphasis of the project is the actual measurement of wear of existing rolls of the traditional "definite chill cast rolls" (0.625" or white iron exterior over grey iron interior), "indefinite chill cast rolls" (a structure between white and grey iron throughout) and the new "niobium enhanced" white iron. The rolls are being measured directly with a "pi tape" (temperature compensated using an infrared detector) at regular intervals (about 2 weeks) during service. Not all types of rolls have been placed in service yet, so no conclusions are available at this time. On rolls which have been monitored, wear has been detected and found to be quite linear with use.
Advancements in Induction Gear Heat TreatmentMr. Neil Merrell, Contour Hardening Inc.
Mr. Merrell is a recent Purdue University graduate, and has been a co-operative student with Contour Hardening Incorporated.
Mr. Merrell presented the advantages of Contour Hardening's "Single Station", "Dual frequency", and "Micropulse" approaches to case hardening gear teeth. By use of a Mid-Frequency heat up, the bulk of the gear tooth is preheated, ensuring that subsequently the "Micropulse" will uniformly case harden each tooth, without "through hardening" which results in a "brittle" tooth and has been a major problem with past induction hardening techniques. The "Micropulse" electronics allow very fast rise times on power which coupled with precision spin and quench control ensures maximum uniformity of case around the gear.
In a typical sequence, a gear is preheated at mid frequency while spinning, translates axially to a high frequency coil for case hardening and is quenched in-place by the coils built-in quenching system. A full cycle takes less than 30 seconds. With selection of appropriate "higher carbon" steels, the case created matches those of traditional carburizing for uniformity, depth, and hardness. Single station operation allow the process to easily integrate into flexible workcells, and just-in-time manufacturing concepts, since it is not a batch process.
Mr. Merrell concluded by showing other developments at Contour Hardening Inc. including a new machine with orbiting coils, allowing customized surface hardening of each section of a drive shaft.
Metallographic Assessment of the Thermal Exposure to the Three Mile Island Unit 2 Reactor Lower Head
Mr. George Vander Voort
The accident at Three Mile Island on March 28, 1979 was the worst nuclear accident in US history.
One of the tasks of the International TMI-2 Vessel Investigation Project was to assess the integrity of the vessel.
By January 1990, it was possible to electrochemically machine coupons from the lower head using a specially designed tool.
This is a progress report on the quantification of changes in both the degree of carbide precipitation and delta-ferrite content and shape in the vessel cladding as a function of temperature and time to refine the estimates of the maximum temperatures experienced.
The lower head of the reaction container was constructed of 5" thick A533B Steel with a 5mm thick #308 Stainless steel claddng. The TMI-2 committee had extracted, decontaminated, and evaluated 15 samples from the lower head using general etching and evaluation procedures. Dr. Vander Voort extended this work by selectively etching the stainless and steel portions, and using programmable electron beam microscopy together with advanced image analysis techniques to refine estimated of temperatures achieved during the accident as well as rates of heat travel during the potential melt down.
Specifically, heating to critical in the steel converted the original tempered bainite structure into "untempered" bainite. In the stainless, temperature could be mapped by the degree of delta ferrite which had spherodized, the amount of an accumulated carbide band (at the steel/SS interface) that was taken into solution, and the size of grains resulting from subsequent grain growth. The path of delta ferrite conversion proved very sensitive to temperature differences in the range of 1050 - 1100C. The volume fraction of carbides was a good indicator for temperature 800 - 1000 C.
The maximum temperature seen by the reactor lower head was about 1100C. This agrees with the findings of the TMI-2 committee. In some samples, the refined metallography found that temperatures higher than originally determined were experienced.
This is a progress report on the quantification of changes in both the degree of carbide precipitation and delta-ferrite content and shape in the vessel cladding as a function of temperature and time to refine the estimates of the maximum temperatures experienced.
The lower head of the reaction container was constructed of 5" thick A533B Steel with a 5mm thick #308 Stainless steel claddng. The TMI-2 committee had extracted, decontaminated, and evaluated 15 samples from the lower head using general etching and evaluation procedures. Dr. Vander Voort extended this work by selectively etching the stainless and steel portions, and using programmable electron beam microscopy together with advanced image analysis techniques to refine estimated of temperatures achieved during the accident as well as rates of heat travel during the potential melt down.
Specifically, heating to critical in the steel converted the original tempered bainite structure into "untempered" bainite. In the stainless, temperature could be mapped by the degree of delta ferrite which had spherodized, the amount of an accumulated carbide band (at the steel/SS interface) that was taken into solution, and the size of grains resulting from subsequent grain growth. The path of delta ferrite conversion proved very sensitive to temperature differences in the range of 1050 - 1100C. The volume fraction of carbides was a good indicator for temperature 800 - 1000 C.
The maximum temperature seen by the reactor lower head was about 1100C. This agrees with the findings of the TMI-2 committee. In some samples, the refined metallography found that temperatures higher than originally determined were experienced.
Dr. Karthik Ramani
Polymer Bonded Systems, Materials, and Mechanics
Dr. Ramani showed many examples of composite materials, including a leaf spring, helicopter blade, orthodonic implant,
othorpedic implant, metal-FRC bonds, and metal-PVP-metal bonds. Facilities at Purdue University's
Composite & Polyment Processing Laboratory include injection molding, pultrusion, controlled adhesive bonding
equipment, and various analytical tools. Polymer-metal adhesives are most effective when the surface is rough on a macro
scale, but smooth in the 30-40 micrometer realm. Anodization is an excellent aid to adhesion for many metal-composite joints.
A process developed at CPPL combining injection molding with induction heating greatly contributes to joint life.
The lab has performed extensive studies of polymer-metal joints and their degradation with time.
Key Points from Dr. Fiore's Presentation, Sept 15, 1997
During the past Fifty years, the materials industry has passed through
three stages of development. As we enter the "Growth" phase in the
21st century, those who succeed will be the companies who focus on
the technology they know best, and expand their presence globally. It
is no longer meaningful to think of one as a "US producer". While some
have viewed Global Competitiveness from a defensive stance, it is really
an opportunity and should be approached with an offensive posture. Suppliers
must position themselves to meet meet demand with fast and dependable
service wherever that demand exists. Options available to alloy producers
to operate competitively in this environment include: alloy development
activities, process research activities, acquired technology
and technological and commercial joint ventures and alliances on a global
basis. A major challenge to the materials industry is the fact that
research in materials takes about 20 years to generate a payback. In the
majority of other industries the cycle is about 5 years, and in software
and entertainment it can be as short as months. To succeed in materials
development takes major capitalization and real staying power.
Present and Future Roles of Aluminum Products in Transportation
Denesh Seksaria P.E. - Technical Consultant - ALCOA Automotive StructuresIn this talk we will look at the use of aluminum in transportation products from a mechanical engineer's perspective. There is a tendency for product engineers to be afraid to get into the unfamiliar. However, designing vehicles of aluminum has been demonstrated to give 40% to 50% weight savings, improve performance, and be more environmentally friendly than most current designs.
The first thing that must be realized is that DIRECT SUBSTITUTION DOES NOT WORK. Aluminum designs will be different from traditional designs because of differences in material properties, manufacturing and joining capabilities. Direct substitution would only be possible when the following questions could all be answered to the affirmative:
Stiff enough?
Strong and durable enough?
Corrosion controlled?
Same paintability?
Same crash loads?
Same vibration and acoustics?
Same manufacturing processes?
Same design principles?
Unfortunately this is not the case.
Elastic modulus: about 1/3 that of steel
Densisy: about 1/3 that of steel
Impulsive strength: Al is not strain rate sensitive while steel is.
Fatigue: about 1/2 that of steel
Ductility: about 2/3 that of steel (less forming range)
Hardness: lower than steel
Thermal Conductivity: about 4 times that of steel
CTE: 13 ppm/F for Al vs 8.3 ppm/F for Steel
Damping: Similar to Steel
Magnetic: None for Al, high for Steel
Electric Resistity: 1/4 as much for Al as Steel
Galvanic Potential: High for Al, Low for Steel
To be successful, aluminum must be incorporated as an integrated MULTIPRODUCT approach. This approach has been successfully demonstrated by ALCOA many times.
Major Factors to be considered are: Cost, Weight, Performance, and Manufacturability.
The multiproduct forms most commonly employed are: Steet, Extrusions, and Castings (sand, die, and investment).
Rolled sheet is best utilized for enclosure surfaces. It can be used either in a heat treated or non-heat treated state. It can be formed by traditional forming (stamping) methods, but specific tool designs must be altered, deep drawing limits are reduced. It may be necessary to split what was one steel component into two aluminum ones. Most traditional joining methods can be employed for Al to Al joints. These methods are usually very low cost.
Extruded Product is an area where aluminum can demonstrate many design advantages. Straight, and curved extrusion with 2D and 3D twist are all possible. When loading condition are predictable, this can lead to many design efficiencies. Al extrusions provide excellent structural performance, and are good in crash tests. Tooling is relatively inexpensive, but processing speeds are slower than formed steel channels. Class A surfaces are also difficult to achieve on aluminum extrusions, and assembly can be more complex due to added stiffness.
Aluminum castings can be made by several processes including sand casting, die casting and investment casting. The quality is dependent on the process chosen. These are used for very complex geometries and usually for thicker sections. Casting are usually used in the heat treated form. Aluminum castings tend to be the most expensive product form.
Joining of alumimum can be accomplished by most traditional methods, (spot welding, MIG welding, adhesive joining, etc.) but the processing parameters MUST BE DRASTICALLY ALTERED. This has led to problems with Al in vehicles where the infrastructure for repair is not educated in these differences.
Six impressive examples of aluminum designs achieving the 40% - 50% weight reduction:
1) The bumper structure of a Buick Riviera using two aluminum extrusion and riveted assembly.
2) Underbody X members of a 98 LH rear suspension using 2 Al extrusions and two Al castings joined by arc welding.
3) Instrument Panel Support (DEW) involving an Al extrusion, Al sheet metal, and a magnesium casting
4) Windshield Surround for '97 Corvette employing Al extrusions, two Al sand castings at top corners, and 2 Al die castings at supports.
5) Prowler Frame combining mostly Al complex extrusions and a few Al castings.
6) Body in White for '92 Mercury Sable using Al sheet metal, with some Al extrusions and some Al castings, joined by spot welding, MIG welding and some quench bonding.
In all of the above cases, the Aluminum designs equalled or out-performed the traditional designs for the same function in all respects, while producing the 40% to 50% weight savings.
Economics, and service infrastructure remain the final stumbling blocks for widespread Al usage in vehicle manufacture.
In conclusion: Aluminum must be applied thoughtfully. Only a multi-product approach is cost effective. Alcoa has the breadth of experience necessary to develop such applications.
Aaron M Scroggin -- Purdue Graduate Student
Development of Pressure Sensitive Paint
Mr. Scroggin's graduate research project is sponsored by Boeing. It is an applications oriented project. In the field of aeronautics there is a strong desire to obtain massive amounts of data concerning localized pressures on aeordynamic surfaces. Typically such data is collected in wind tunnels using "pressure taps" (sensors which are individually mounted in carefully prepared arrays of holes). This is a very costly process and limits data to the exact location of each "tap".The thrust of Mr. Scroggin's work is to use luminophores in an applied layer on such aeronautical structures to enable the collection of data from infinitely resolvable points, and at the same time dramatically reduce costs of test preparation.
Luminophores are materials that absorb radiation to go to a higher energy state. Typically such material will return to its base state with the emission of a photon, at a wavelength longer than the original radiation. If a luminophore is in contact with oxygen, it excites the oxygen which can take on the energy without alowing the photon emission. This characteristic is referred to as oxygen quenching. Since the "oxygen quenching" effect is proportionally related to the partial pressure of oxygen, the brightness (emission of photons) of the luminophore is inversely related to pressure. Thus luminophores are potentially useful for monitoring pressure on a materials surface.
Prior work has put luminophores into polymers to create a "paint". Unfortunately, the polymers drastically diminish the response time for photon emission. However, if luminophores can be integrated into ceramic coatings the response time will be nearly instantaneous. This is the thrust of this project.
In the experimental stages, alumina particles were coated with a very active luminophore. These were then "tape cast" into a flexible and easy to handle film down to thicknesses as low as 0.01 mm. Strips of this film were applied to the wing and other aerodynamic surfaces of Purdue University's executive plane. During a flight test the tapes were excited by a scanning laser light system and photon emissions were captured to a computer for analysis.
The actual data collected was less than desirable. One of the tapes peeled off of the wing. Another problem is the fact the the photon emission is strongly related to temperature as well as to pressure. Some way of compensating for or mitigating this effect must be found.
Next steps for the project will be to develop tapes for use at cryogenic temperatures (where aeronautical types can use small models to represent large structures), and to quantify photon emission with respect to binder content in the tapes.
Marc Yap -- Purdue Graduate Student
Titanium Powder Metallurgy for Spinal Implants
In the human spine there are 23 articulating vertebrae and 9 fused. When a disc requires repair the current practice is to encourage interbody fusion between the adjacent vertebrae. The design criteria for such repair is replacement of the damaged disc with new bone growth, and to restore the interspace.Early fusion methods called packing relocated bone between the vertebrae. Complications of this method included pain, collapse, and settling. This was followed by using rigid interbody spacers and posterior rods. These, however, frequently failed from fatigue loading. Next came the bone dowel (which was more rigid than the packed bone) and then the concept of the threaded diffusion cage (a porous metal dowel packed with bone).
The emphasis of this research is material development for a new surgical mesh (in a trapezoidal [wedge] shape) which will be an improvement on the threaded cage. The porous wedge holds position better than the dowel but is much more expensive and difficult to manufacture.
Titanium and specifically powder formed titanium alloys offer great potential for the trapezoidal surgical wedge because of their low elastic modulus, biocompatability, and ease of manufacturing to near net shape. A potential improvement to the technology is the development of a "dual density" wedge. This is easily accomplished by multiple sintering operations of the formed powder, and offers the advantage of a fairly dense and strong outer load bearing shell, with a much more porous inner ring. (The added inner porosity can be optimized for ingrowth of new living bone while providing high strength and a low modulus). At this time the demonstration has been restricted to simple geometric shapes, but the dual density titanium P/M technology should easily transfer to the more complex surgical wedge. This work is in need of sponsorship. If interested, please contact Dr. Matthew Krane, School of Materials Engineering, Purdue University.
What's New in MetallographyPatrick Foster
LECO Corporation
The main focus at LECO corporation and particularly in the Application's Lab is in metallographic sample preparation. The LECO strategy has not been toward "full automation" but rather to preserve a balance between efficiency, improvement of results, and the "Human Factor", since it is recognized that ultimately there will always be a human evaluating what a metallographic laboratory facilitates. At one in the same time, the "Human Factors" which lead to less consistancy of results are being minimized.
The most significant advance in sample preparation is a 3-M LECO introduction of TRIZACT abrasives. Traditional sample preparation papers are SiC and have several inherent disadvantages. Due to great variation in particle height on the SiC paper, they tend to be very agressive on initial contact with the sample, and wear out rapidly (usually in 20 - 30 sec). Because of this a whole series (usually 120 180 240 400 and 600) of abrasive sizes must be used to bring any one sample to the polishing stage. TRIZACT abrasives are radically different. Particles are shaped (as discrete pyramids) on the backing and have an entirely uniform height and cutting characteristic. Grinding is a very uniform operation (it is neither "very agressive" on first contact, nor becomes ineffective after several minutes). Because of this, a sample can often be taken from "raw cut" down to "ready-to-polish" on one single TRIZACT faced cloth. Moreover, the cloth is
usually good for about 30 minutes (not seconds) of grinding, so many, many (about 80) samples can be prepared on the same cloth. After the 30 minutes of grinding time, the backing cloth (a different color) shows itself as a color change, indicating the TRIZACT is now worn out. While costing about 5-6 times (per sheet) what SiC does, it can be readily shown that using TRIZACT ultimately reduces good sample preparation costs from about $0.46 / sample to $0.08 / sample accounting for time saved, as well as extended media life.
Using TRIZACT will require a learning curve, since cutting is so uniform. Actual grinding time is less (about 120 - 180 sec / sample), (compared to the time spent on 5 SiC papers) but seems longer since it is not split-up on five media with an initial aggressive surge of removal. Technicians require considerable experience with the media to get used to this concept. The main differences are: 1) the media will wear down evenly 2) there is less vibration and "feel" to the process 3) there is less stress (grabbing) of the sample. 4) the only lubricant required is water (only enough to flush debris). TRIZACT works well with most metals, alloys, and coatings EXCEPT aluminum. Aluminum will tear up a TRIZACT cloth almost immediatey.
Another improved approach to sample preparation is something LECO calls "Linear Sectioning" and is applied to its new line of Cut off and sectioning equipment. Most recent equipment has used a "plunge" approach, in which the cut-off wheel is plunged into the stock. With "linear sectioning" the stock is traversed in the cutting line of the wheel, and multiple passes are made (if necessary) to complete the cut. This "cutting line" motion is referred to as the X-axis. Z-axis (plunge) indexing is used to do multiple passes, and Y-Axis (perpendicular to the cutting line) indexing is used to make multiple parallel cuts (if required). This approach has been found to do a much better job on large irregular shapes, and combined with the availablility of variable blade speeds both minimizes deformation and speeds up the cutting process. Elimination of "burning" reduces work in subsequent grinding.
(REVIEWERS COMMENT: none of this is new -- when I began my metallography work 27 years ago, such equipment was in common usage, [ie. table saw, or radial arm saw style cutting which achieves the same result] however; nothing [particularly the operator] was protected from dissintegrating blades, flying chips, etc. The safety factors present in today's equipment were not in place.)Since "enclosed" cutting is now available in this style, LECO has been able to go to much thinner blades (which while fragile) greatly improve microsectioning efficiency.
In the area of "automation" of Grinding and Polishing, LECO has choosen to produce a line of equipment which is "modular" and easily "upgradable". A basic wheel, is the core. A solid state speed control can be the first module. This module can be replaced by a multiple sample manipulating "head" with automatic control from a LCD control screen; and ultimately basic "wheel" units can be linked together (two wheels sharing one sample head) into a chain, for nearly total automation. At any level, the same "modules" are used and the original investment in the "wheel", or "head" modules is never lost.
LECO has introduced a "new generation" of microhardness testers, from "fully automatic" to a "semi-automatic" (which actually is faster than the "full automation" unit). The "semi-automatic" does indentions per a program schedule and downloads the images to a computer screen for "user assisted" measurement, and the final results to a spreadsheet for useful analysis and archiving.
Finally, microphotography, is rapidly moving in the direction of digital images. Such images are now beginning to rival those of traditional photography, and are much more convenient for storage, archival, and retrieval than the old file of polaroids.
Precipitation Hardened Stainless Steels -- New Alloys and ApplicationsFred McMann
Carpenter Specialty Alloys
Carpenter Specialty Alloys is a global supplier of an extemely diverse set of metals and alloys. It is seeking recognition as the one-stop-shop for all metallic needs. Despite the global nature of its marketing and distribution system, virtually all of its alloys are produced in the U.S.A. and to the highest possible industry standards.
Precipitation Hardening Stainless Steels have been around a long time. They are know for thier martensitic structure. These alloys are based on Chromium and Nickel, with the addition of additives to promote a precipitating phase such as Titanium. The treatment of these alloys involves 1)Solution Annealing (also referred to a Quenching or Condition A), 2) Precipitaion Hardening (also referred to as Aging or Tempering or "H" Condition).
Recently, Carpenter came out with a new PH Stainless "Custom 465" which was originally developed for an aircraft application. It is the strongest of all Stainless Steels in the "PH" family (>255,000 psi in the H900 condition). This exceeds it predecessor (Custom 455) by about 10,000 psi. In most aged conditions it is also superior to other PH Stainless Steels in fracture toughness (about 110,000 psi).
Funding was lost for the original application of this alloy, but it has found a new and very successful market in the golf club head industry. The much publicized Orlimar Trimetal clubs use Custom 465 for the face. The alloy was not selected so much based on mechanical properties, but rather for its unique sound as it strikes a golf ball. Other applications are expected to follow.
Another recent Carpenter Development is AerMet, which is quite simply the highest combination of strength and toughness of any metal alloy known to man. It achieves maximum hardness of about 55 HRC and tensile of 310,000 psi with an age treatment at about 875 F with ductility around 17%, and fracture toughness of about 90,000 psi/in-2. With higher aging temperatures, fracture toughness can exceed 150,000 psi/in-2 with some loss of strength. Its introduction won distinction for Carpenter as one of the ten most significant inventions of its year.
Besides its optimized composition, AerMet achieves its remarkable properties by being Vacuum melted three times, during its production. It is extremely clean and free of sulfur and other contaminates. In fact, while it has a crystalline microstructure, it is virtually impossible to bring out any grain boundries by conventional metallography, since it is so very clean. This enables remarkable toughness and impact properties for a very strong material. The biggest drawback to AerMet is its high cost of production, which is about 5 times that of typical tool steels.
AerMet has found usefulness is very demanding tool steel applications such as: punches, blanking dies, crimping dies, collets, chuck jaws, shear blades, coining dies and swaging tools, where longevity of service is of primary importance and the high cost can be justified.
Options for Training Employees for Better Heat TreatmentSandy Cioletti
Manager of Education and Training for the Heat Treating Network
The Heat Treating Network is a non-profit, member-driven national association headquartered in Cleveland, Ohio whose mission is to enhance the image, practices, and profitability of the heat treating industry through education/training, technology transfer and problem solving services. With a focus on education, the Heat Treating Network developed different levels of education and training systems specific to the heat treating industry. From entry level training for new hires, to continuing education programs for seasoned personnel, to a formal Heat Treater Apprenticeship; the Heat Treating network has programs and materials to meet the need for developing knowledgeable and skillful employees in the heat treating industry and in-house heat treating departments. Informative educational seminars on specific aspects of heat treating are also available.
Specific training options are arranged by the Network into a five level pyramid.
At the base level are "Entry Level Training" tools, which are various self-study options designed to familiarize newly hired heat treaters with the equipment and processes they work with. Emphasis is on equipment and safety.
The second level includes "Seminars, Workshops, and Videos", designed for short term concentrated study and providing good fundementals of a variety of heat treating topics.
The third level is "Independent Study Courses". These are formal studies in various heat treating topics which the student can take at his own pace. They are provided by ASM International, and are the MEI Home Study materials. The offerings include: "Induction Heating", "HT Quality and Inspection", "Principles of Metallography", "Heat treatment of Steel", "Practical Heat Treating", "Principles of Heat Treating", and "Maintenance of HT Equipment".
The fourth level is "Customized On-Site Training". The Heat Treating Network is very experienced in putting together the people and resources to provide this "just what's needed" approach to training within the workplace.
The top level is the "Apprenticeship Program". This four-year program consists of 576 hours of classroom instruction and 8,000 hours of on-the-job skill training. It meets the requirements of the U.S. Department of Labor - Bureau of Apprenticeship and Training, and of SAE specification ARP-1962. Completion of training entitles certification as a Journeyman of Heat Treating by the State where apprenticed. All arrangements and administrative details are handled by the Heat Treating Network.
Micromachines: An Enabling Technology for the FutureDr. Alton Romig Jr.
President ASM International
Director, Microsystems Science, Technology and Components, Sandia National Laboratories
When one defines a "microsystem" one can consider a small living creature, such as a dust mite. Six characteristics that are present in the "system" are: Sensors, Intelligence (processing capability), Actuators, Power, Communication, and Self-Assembly. It is now possible to incorporate all of these characteristics into a single piece of Silicon; a multifunctional "system-on-a-chip" which can Sense (smart sensors), Think (process info - custom microprocessors), Communicate (laser optical), and Act (MEMS and IMEMS [Intelligent] Miniature Electro-Mechanical Systems).
Virtually, all components of such systems are batch fabricated onto a single silicon wafer, and require no assembly, making mass production very inexpensive. Monolithic parts are also extremely reliable. Process development (on the other hand) is very expensive. The fabrication process for the MEMS involves the following seven steps (repeated many times depending on complexity of the chip design). It is performed seperately from traditional CMOS processing on the same silicon wafer, by processing the wafer in a modular fashion.
1) Deposit layer of sacrificial oxide on single-crystal Si wafer.
2) Apply light sensitive photoresist, and expose using oxide mask of detail.
3) Develop the photoresist and etch away oxide not protected by the photoresist.
4) Strip off photoresist and deposit conformal layer of polysilicon.
5) Apply photoresist, and expose using polysilicon mask.
6) Develop the photoresist and etch away polysilicon not protected by photoresist.
7) Strip off photoresist and etch away sacrificial oxide to complete the feature.
An example of this technology being developed is "smart airbag sensors" which incorporate multi-axis accelerometers, a processor, and mechanical-photo latching to execute a "controlled" deployment of an airbag, in response to the nature of the impact, weight and trajectory of the passenger, etc. Other likely uses include Medical Pressure Sensors, Automotive Pressure Sensors, Smart Tires, ABS Sensors, Auto Navigation Gyros, Smart Munitions, Pacemakers, Machine Monitoring, Machine Control, Infusion Pumps, Industrial Valves, Fluid Meters, Ink-Jet Printers, and Optical Switches.
Details of Radiation Hard Sensor and MEMS working as an on-board weapons lock were presented. The device, which requires a 24-bit key code, is only 4 mm x 4 mm and is uneffected by radiation or EMF.
Magnequench ProcessingMr. Mitchell Spencer
Magnequench Corp., Anderson, IN
When the oil valve was turned off by the OPEC cartel in the mid 1970's, there was a strong incentive for weight reduction in automobiles. General Motors discovered that NdFeB (Neodymium-Iron-Boron) provides much superior magnetic force for weight. Out of this discovery, in 1986 GM opened Magnequench as a production facility for the new magnets to be used in cranking motors.
Unfortunately, early NdFeB magnets did not receive much acceptance in the automotive industry, so in 1995 GM spun off the company, which by then had found many new markets for its products, most importantly small motor magnets in devices like floppy drives, hard disk dries, and read/write motor control in the computer industry and stepper motors in other equipment.
Currently NdFeB magnets comprise about 33% of the entire magnet market. This is expected to rise to 50% by 2005. The largest market share belongs to Japan, followed by China, and then the USA (primarily Magnequench).
Magnequench magnets can be made in complex net shapes, and with thin walls if necessary. The best grade of NdFeB magnets can be as much as 40 megagauss-oersted (which is about 10 time that of ferrite magnets and about 4 times that of platinum-cobalt, the next best magnetic material). Magnetism is maintained up to about 600F in NdFeB magnets, however binders used to form the shapes are susceptible to failure at lower temperatures.
Magnequench uses three processes to make its magnets:
All three processes begin with the reduction and separation of Nb from a neodymium oxide / calcium / calcium oxide mixture with calcium in the molten state. The raw neodymium is then alloyed with iron in about a 20/80 eutectic ratio, and refined in a vacuum induction furnace prior to casting an ingot. This alloy is then remelted in a melt spinner and undergoes rapid solidification on a quenching wheel to form a ribbon which is ground to become the primary source material.
The MQ1 process makes the most versatile, and least expensive magnets. The raw material is mixed with a thermoset epoxy and molded into any shape needed. The last step is magnetization (usually performed by the customer) which involved the discharge of a large capacitor bank such that the flux field intersects the parts to be magnetized. The magnets are (of themselves) isotropic.
The MQ2 process produces a stronger magnet and no binder of adhesives are added to the magnet material. Instead they are hot compacted under controlled conditions to form isotropic parts.
The MQ3 process is a continuation of the MQ2 process, in that hot compacted billets are directionally forged in order to obtain a specific alignment of grains. These materials are anisotropic, but also have the highest magnetic densities of any material known.
Magnequench hopes to open a plant in China in the next few years to avoid the transportation costs for the neodymium, most of which is produced in China anyway.
Converting Star Wars Technologies to Material ProcessingDr. Glenn Whichard - UTRON Inc.
UTRON, Inc. personnel began developing new gun launch technologies under the Reagan Strategic Defense Initiative in the 1980s. Methods to accelerate projectiles, such as the electric light gas gun, combustion light gas gun, ram cannon, rail gun and electrothermal/electrochemical ignition systems were invented. When the Cold War ended defense funding for these programs was cut significantly. UTRON, Inc. turned its attention from defense to applying these high acceleration technologies for commercial processes and products.
UTRON has been particularly active in the replacement of solid propellant with gasses as in the Electric Light Gas Gun which launches projectiles as fast as 7 km / sec. Commercial Spin-offs from this technology are being developed in four areas of material engineering. Polymer Coating, Impact Bonding, Consolidation of Powders, and Fine Metal Powder production (nano materials).
In the area of "Consolidation of Powders" a technique referred to as CDDC (Combustion Driven Dynamic Consolidation) has been developed. Generally the gasses combusted are hydrogen and oxygen. The technique allows control of 1) Pressure rise rate, 2) Pressure Peak, 3) Duration, 4) Energy, and 5) Temperature. While still highly developmental, Aluminum powder has been consolidated to 98% of theoretical density at ambient temperature. Forming pressures as high as 500 kpsi are reached. It is hoped this technique will permit production of near net shapes from unusual alloys.
For impact bonding (coating) UTRON is developing a technique called PHAST (Pulsed High Acceleration Spray Technique). This technique developes a high pressure gas charge within a barrel. When the barrel is opened a pressure front moves back as pressure is released. Powder is fed and ignition (by capacitor discharge) of a plasma jet is timed to propel the powder outward at maximum velocity (> 2000 m/sec). With this velocity coating can be formed below the melting point of the coating materials which means low oxide contents. Currently the major limitation of the process is the relatively long time required to recharge capacitors, limiting the pulse rate. This should not be difficult to overcome, however. A variant of the process feeds solid fine wire instead of powder in front of the plasma jet. Results are similar but velocities are somewhat lower (1260 m / sec).
In the area of atomization a molten metal stream is fed in front of a plasma jet similar to that described above. The charge is dispersed into a collection chamber for the atomized powder. The atomizer is typically run with inert (Argon) gasseous atmosphere at about 40 pulses / sec. Highly spherical fully dense particles are formed with a broad distribution of sizes from 3 nanometers up to 5 micrometers (pure copper example). Currently the process can produce about 3 Kg of powder in 18 minutes. Development will be aimed at increasing the yield of nanoparticles from the process.
Little Things and Big Pictures: ongoing research and new materials research projects at PurdueDr. Alexander H. King - ASM Fellow - Purdue University Material Dept. Head
We will be looking at some of my personal research "Little Things" studied with electron microscopy, and then at some of the new initiatives happening in material engineering at Purdue University "Big Pictures".
Since very early in my life I have had a passion for the study of the unseen "little things". It is quite natural that I have found the study "Interfaces" (the infinitely divisible junction between two materials) to be my primary research focus. The tools for such research are the "electron microscope", particularly the TEM (transmission electron microscope) and the computer for modeling.
[Dr. King's presentation includes numerous SEM and TEM photomicrographs which cannot be shown here. We will simply highlight some of the conclusions he has reached as a result of his studies. - webmaster]
A very interesting study is the deposition of Zirconia on polished stainless steel. Many would say that a "splat" of Zirconia would not stick to a non-roughened stainless surface without a bond coat but actually the opposite is true. The interface between Zirconia spats and polished stainless is actually stronger than with a prepared surface. At the interface, four layers exist. From outside to base metal these are: the Zirconia, an interfacial oxide, resolidified substrate, and base metal (substrate). There is some lateral cracking due to thermal expansion mismatch. This can be controlled and predicted with the parameters: CTEs (thermal expansions), temperature of substrate, and fracture toughnesses. When the "splat" of Zirconia is applied to a roughened stainless surface, an "ingot" structure is formed where the Zirconia penetrated a cavity in the roughened stainless. Like all "ingots" there is a shrinkage cavity with forms on cooling, but in this case the cavity forms on the outside of the cast structure (breaking the bond with the stainless) rather than at the top center (as in gravity casting). Because of this broken bond, the splats on the roughened surface are much more weakly bonded than those on the polished surface.
Another interesting finding in the world of interfaces is demonstrated when ZrO (zirconia) splats are bonded to prior ZrO splats. Looking at the "structure" of such a bond, it appears that "columnar crystals" exist as a uniform entity right through the interface yet contradicting this; is the fact that the interface is a weak area and the structure will predictably break right at the interface when stressed. Detailed study has revealed that exactly at the interface there is a mixture of crystalline and amorphous ZrO which allows the crystalline growth to continue (without grain boundary) through the interface, but this is accomplished with only small points of contact within the tiny amorphous/crystalline layer. The same effect can be demonstrated with the epitaxial formation of SiC on Si at low temperature.
A final observation in the realm of "small things" is the study of "triple junctions". From the observations of a Grad student, it was observed that individual grains can actually "rotate" within a crystalline structure. The process is slow, but can be shown to involve diffusion at the corners of the grains (specifically the "triple junctions"). Bismuth diffusing into Cu can be used as an illustration of this concept. Dr. King has developed a mathematical model for this phenomenon.
In the area of Big thing at Purdue there are several new programs:
TAP; is the Technology Assistance Program available to Indiana businesses with needs in the area of materials problems.
A "new undergraduate curriculum" focuses initially on "practical" production and use of materials and then progresses into "theory" instead of the traditional "reverse" approach.
For "senior projects" students work with industrial partners to solve real problems. This involves considerable commitment on the part of the industrial partner, but the benefits are usually quite high.
New facilities are planned for Miltidisciplinary Engineering (including materials) and for Nanoscale Fabrication.
Under an Electron Microscopy Management Plan, "electron microscopes" will be selected for unique "state-of-the-art" capabilities for use by all science/engineering disciplines, rather than maintaining "redundant" equally capable units dedicated to individual disciplines.
A Materials Consortium is being formed to coordinate all schools with involvement in materials.
The 21st Century Fund, is available from the State for joint industry/academia research projects. The approval process is fairly streamlined.
Analyses of a Thermally Grown Oxide Scale in Thermal Barrier Coatings Containing a Platinum-Nickel-Aluminide BondcoatMichael R. Brickey - Purdue Graduate Student
Hot running turbine engine components made of such alloys as Rene N5 are treated with bondcoats of Ni, Pt, and Al alloy for oxidation protection. To prevent melting, the coated component is also coated with an insulative barrier coating of Yttria Partially Stabilized Zirconium (YPSZ). Between the two coatings, a very fine layer of "TGO" (Thermally Grown Oxide) is present. The initial development of this thin oxide layer is the topic of this presentation.
Most prior research has assumed this layer to be Al2O3. The bulk of this study was performed by CTEM and STEM studies of this layer, first at its initial state (immediately after deposition) and after up to 10 thermal cycles simulating use of the turbine.
In the initially deposited state, there was concern that metastable forms of oxide might be present. However, none were found. All of the Al2O3 detected was found to have the stable hexagonal structure.
Near the YPSZ layer there were increasing concentrations of ZrO2 found in the oxide layer. These were present as dispersoids with an average diameter of 0.03 micrometers.
In thermally cycled specimens, a "duplex" structure was noted. Near the YPSZ side, ZrO2 dispersoids were frequently present and the structure was equiaxed (rather than the columnar structure of the YPSZ iteself). Futher toward the bondcoat the structure was columnar and free of ZrO2. The equiaxed layer is probably the result of nucleation and growth of Al2O3 around ZrO2 at pinning sites within prior existing columnar grains. Recrystalization occurs to relieve stress.
It would be desirable to eliminate this region and the dispersoids which cause it. The author proposes two methods: 1) addition of a diffusion barrier coating (but this would further complicate the overall structure), or 2) using tailored surface preparation to discourage Zr migration to the TGO layer.
Evaluation of Milling Cutter Weld Processing Failures and Other Selected Projects from TAPThomas R. Kanaby - Purdue Graduate Student
The Purdue TAP (Technical Assistance Program) is a state funded outreach of Purdue University to provide Indiana businesses access to University expertise and facilities for the solution of engineering problems otherwises beyond their reach. The program has been successful in saving such businesses considerable production related expenditures and at the same time saving jobs for their workers.
The Materials Engineering Dept. at Purdue participates in TAP in three ways.
1) Material Selection Assistance
2) Corrosion Study and Failure Analysis
3) Process Analysis
One particular project of this third type is the topic of this presentation. It involved a company that had been for years successfully resistance butt welding M4 tool steel mill cutters to 4140 shafts. Upon retirement of the person performing this weld, the company found that it could not train new operators to achieve a reliable weld using the same equipment. Detrimental cracks were usually present. The task of TAP was to make the process "more flexible" and less operator dependent.
Initially the process was reviewed. It was found that a fixed amount of current was applied through the abutting metals, and at a given amount of collapse (1/4") the operator released a foot pedal stopping the current. There was little desire by the company to spend money on changing equipment or the basic process which had been successful for over 30 years.
Next the weldments were examined. The defective ones were found to have a continuous crack in the M4 steel adjacent to the weldment. Hardness and microscopic work indicated the M4 near the weld interface was in a metastable state, while the 4140 was relatively unchanged from parent metal.
Three suggestions were sequentially made to deal with this problem.
1) use "slow cooling" (this was not pleasing to the company as production efficiency would be adversely effected, and it was found it didn't work anyway).
2) Offset the weld such that the M4 would be heated less. This was accomplished by making the cross section of the M4 large (relative to the 4140), shifting resistive heat away from the M4.. This added "bloom" of material would later be machined away. Like the first solution, this did not work.
3) Do the reverse of method 2 -- that is force higher heating of the M4 in hope that the crack would be "expelled" from the weld joint since the highly heated material would be displaced to the side. This was accomplished by adding a "projection" to the M4 of smaller diameter than the 4140 abutting it. This method proved to be successful. An interesting observation is that the crack which occurs in the excessively heated M4 actually "turns away (U-turn style)" from the central portion of the weldment and remains at the outer extremities of the weldment diameter. Acceptable parts are created by this method, saving the company considerable investment in new technology.
Corrosion Resistant Nickel Alloys
Paul Crook -- Haynes International Inc.There are five main categories of usage for Nickel based corrosion resistant alloys.
1) Chemical Processing (in situations where stainless steels don't work.
2) Pollution Control - particularly in flue gas desulfurization.
3) Pharmaceuticals
4) Agrichemicals
5) Waste management (particular radiactive waste management).
In a hierarchy of corrosion resistant alloys the "nickel alloys" together with "zirconium alloys" and "titanium alloys" serve in special situations where stainless steels cannot perform and greater expense is justified. The ultimate in corrosion resistance is reached with "tantalum" but due to high cost, its use is restricted to the most critical of situations.
The main attributes of the Corrosion-Resistandt Nickel Alloys include:
-- high resistance to stress corrosion cracking
-- many resist aggressinve reducing acids (ie. hydrochloric, hydroflouric, and medium concentrations of sulfuric.
-- some withstand both strong reducing AND strong oxidizing acids.
-- Many exhibit high resistance to alkalis
-- Some have high resistance to pitting and crevice corrosion.
-- All are ductile, and easily formed and welded.
The main groups and used of corrosion-resistant nickel alloys are:
-- Ni alloys (for alkalis)
-- Ni-Cu alloys (for reducing acids)
-- Ni-Mo alloys (for reducing acids)
-- Ni-Fe-Cr alloys (for oxidizing acids)
-- Ni-Cr-Si alloys (for super-oxidizing acids)
-- Ni-Cr-Mo alloys (for alkalis and all acids)
Mr. Crook then when on in considerable detail explaining the development of a "Decision Tree" which selects an appropriate alloy for various specific application environments. Included in the decision are acid types, concentrations, purity, temperature, presence of other ions (impurities) etc.
This decision tree is to become available soon at the Haynes International web site www.haynesintl.com.
The entire presentation (including the "decision tree") is also available in printed form by request to the speaker (800) 354-0806.
Endothermic Atmosphere Chemistry and Control
Allen Golden - Surface Combustion Inc.What is "endothermic protective atmosphere"?
In simplest terms it is 40% Nitrogen, 40% Hydrogen and 20% Carbon Monoxide (when made from Natural Gas "Methane" and Air). It can also be generated from propane and other hydrocarbons, with slightly different resulting compositions.
It is the result of reacting one volume of Methane with one volume of air and results in seven volumes of Endothermic Atmosphere.
The reaction takes place in two stages. In stage one the reactants yield Water, Carbon dioxide, and Nitrogen along with excess methane. It is performed by heating the reactants to around 1850 - 1900F over and alundum media in the reaction tube.
The transformation is completed over a nickel catalyst in a second stage of the reaction tube which breaks up most of the water to form hydrogen gas and combines the water's oxygen with the additional methane to produce Carbon Monoxide and additional Hydrogen gas.
The actual final composition of the endothermic atmosphere is approximately: 37.9% Nitrogen, 40.6% Hydrogen, 20.7% Carbon Monoxide, with 0.1% Carbon Dioxide, 0.3% Water, and 0.4% Methane remaining in the stream.
Both the Dew Point (water content to temperature relationship) and Carbon Dioxide content can be used to relate to the carbon potential of the atmosphere, which is a major factor in determining case hardening effectiveness for ferrous alloys.
Modern "Endothermic Generators" include features to reduce maintenance, such as filter systems for pump lubrication (requiring only yearly change), air cooling (as an option vs. a water system), separate heaters for each reaction tube which allows "burn-out" (reduction of carbon deposit) of the catalyst of one tube while others continue to generate gas, and automated control of "Dew Point" via oxygen probes.
Surface Combustion recently participated in a study requiring "very tight" control of case depth through better control of the endothermic atmosphere. The goal was to reliably produce coupons with +/- 0.05% maximum deviation of carbon from the set point of the endothermic controller.
The study was conducted over a wide range of temperatures, and set points using batch "integral quench" furnaces at a Texas oil well bit manufacturing facility with carbon ranging from 0.2% up to 1.1%.
When controlled with only "oxygen probes" for dew point the deviation was much to great (+/- 0.2%). Therefore, and IR analysis system with feedback for control was added to the generator system. This system could acurately measure Carbon Monoxide, Carbon Dioxide, and Methane content of the gas.
It was found that using theoretical calculations and on-line Carbon Monoxide and Carbon Dioxide results from the analyzer, it was possible to obtain the +/-0.05% carbon accuracy over 90% of the time. (Final verification of the carbon was by measuring carbon in actual metal samples carburized during the gas generation periods using a LECO carbon analyser).
An interesting point of the study was that when IR Methane analysis was added to the control parameters, the accuracy of the control set point to LECO measurement actually went down, and the +/-0.05% parameter could only be held about 40% of the time. This would suggest that "methane content" should be monitored (as it serves as an excellent indicator of problems and maintenance cycle for the generator), but it should NOT be figured into the control parameters.
October 18, Purdue Labs Tour
We took the bus to West Lafayetteand Arrived at the School of Materials Engineering
Had yummy snacks with our new Chapter members from Purdueand had a great tour including an injection molding demonstration.
Nickel and Cobalt Alloys for High Temperature Service
Rodger Seeley - Haynes International Corp.First we will address "What are high temperature alloys?" Why are Crome Nickel and Molybdenum key alloying elements?
High temperature alloys are generally used above 1000F (538C). They are specifically designed to withstand heat. Key properties for such applications are 1) High Temperature Strength, 2) Limited Scaling (corrosion), and 3) good thermal stability over time.
Specific properties considered for high temperature applications include Fatigue, Creep, Tensile, High Temp corrosion, Out-of-service corrosion, erosion, thermal stability, and physical properties.
The three basic families of high temperature alloys are Nickel base, Cobalt base, and Iron base. The Nickel base alloys are further classified as Solid Solution Alloys and Age Hardening Alloys. The elements Cr, Si, and Al are used in high temperature alloys to impart corrosion resistant properties. Al, Ti, and Nb are used in the age hardenable alloys to form strengthening percipitates. W and Mo are added to increase strength in solid solution alloys. Rare earth elements, (such as La and Y) are added to stabilize scales. Nb, Ta, Ti, and Zr are added to stabilize carbon. Finally the elements carbon and nitrogen are used to increase creep strength.
Nickel base solid solution alloys are noted for excellent resistance to carburization, chloride and oxidants attack, and also for good high temperature strength. The Nickel base precipitation hardening grades offer the highest strengths but are limited to intermediate temperature service. Cobalt based alloys offer excellent wear resistance, creep strength, and best sulfidation resistance. The iron based alloys are easier to fabricate, have good creep strength, and are also sulfidation resistant.
Some applications for high temperature alloys include rotary kiln parts, calcinators, refuse burners (particularly in superheater portions), fans for high temperature and corrosive gasses, and gas turbine combustors.
Some material properties become particularly important when considering high temperature applications. One of these is creep. Creep is the deformation of the metal with both temperature and TIME considered. It occurs in three stages. Stage 1 is an initial high rate deformation. Stage 2 is characterized by a uniform rate of deformation over a relative long period of time. Stage 3 is similar to regular tensile failure with rapidly increasing deformation until final rupture. Creep has three methods of measurement. 1) "Rupture life" is the TIME, STRESS, and TEMPERATURE which result in a rupture. 2) "Creep Rate" - is the rate (change in length per unit time) of deformation during Stage 2 of the creep. 3) "Creep Life" is the TIME, STRESS, and TEMPERATURE needed to cause a defined amount of deformation (short of a failure).
Fatigue is another property which has special implications in high temperature service. Low cycle fatigue in measured by the repeated application of a specified amount of strain at a stated temperature until failure. The cycle count is the value reported. High cycle fatigue is usually measured by repeated stress to failure, and is more significant in lower temperature applications. It is generally reported as a the stress level which reaches a certain cycle count limit.
Thermal Stability is yet another property very important to high temperature service. It is measured by common ductility measurement methods except after prolonged high temperature exposure periods.
Haynes has not found that simple weight gain or weight loss provide a good measure of High Temperature Corrosion by oxidation. Instead we employ a metallographic technique whereby metal loss from both surfaces is added to either the average penetration of oxides into the metal, or the maximum penetration of oxides into the metal. The first measure is referred to as "Average Metal Affected", and the later is "Maximum Metal Affected".
(Editor's note: Mr. Seeleys talk included numerous charts and graphs illustrating the above characteristics and comparing numerous alloys. For copies of this extensive data, please contact him at Haynes Inernational Inc.) rseeley@haynesintl.com
Present and Future Roles of Aluminum Products in Transportation
Denesh Seksaria P.E. - Technical Consultant - ALCOA Automotive StructuresIn this talk we will look at the use of aluminum in transportation products from a mechanical engineer's perspective. There is a tendency for product engineers to be afraid to get into the unfamiliar. However, designing vehicles of aluminum has been demonstrated to give 40% to 50% weight savings, improve performance, and be more environmentally friendly than most current designs.
The first thing that must be realized is that DIRECT SUBSTITUTION DOES NOT WORK. Aluminum designs will be different from traditional designs because of differences in material properties, manufacturing and joining capabilities. Direct substitution would only be possible when the following questions could all be answered to the affirmative:
Stiff enough?
Strong and durable enough?
Corrosion controlled?
Same paintability?
Same crash loads?
Same vibration and acoustics?
Same manufacturing processes?
Same design principles?
Unfortunately this is not the case.
Elastic modulus: about 1/3 that of steel
Densisy: about 1/3 that of steel
Impulsive strength: Al is not strain rate sensitive while steel is.
Fatigue: about 1/2 that of steel
Ductility: about 2/3 that of steel (less forming range)
Hardness: lower than steel
Thermal Conductivity: about 4 times that of steel
CTE: 13 ppm/F for Al vs 8.3 ppm/F for Steel
Damping: Similar to Steel
Magnetic: None for Al, high for Steel
Electric Resistity: 1/4 as much for Al as Steel
Galvanic Potential: High for Al, Low for Steel
To be successful, aluminum must be incorporated as an integrated MULTIPRODUCT approach. This approach has been successfully demonstrated by ALCOA many times.
Major Factors to be considered are: Cost, Weight, Performance, and Manufacturability.
The multiproduct forms most commonly employed are: Steet, Extrusions, and Castings (sand, die, and investment).
Rolled sheet is best utilized for enclosure surfaces. It can be used either in a heat treated or non-heat treated state. It can be formed by traditional forming (stamping) methods, but specific tool designs must be altered, deep drawing limits are reduced. It may be necessary to split what was one steel component into two aluminum ones. Most traditional joining methods can be employed for Al to Al joints. These methods are usually very low cost.
Extruded Product is an area where aluminum can demonstrate many design advantages. Straight, and curved extrusion with 2D and 3D twist are all possible. When loading condition are predictable, this can lead to many design efficiencies. Al extrusions provide excellent structural performance, and are good in crash tests. Tooling is relatively inexpensive, but processing speeds are slower than formed steel channels. Class A surfaces are also difficult to achieve on aluminum extrusions, and assembly can be more complex due to added stiffness.
Aluminum castings can be made by several processes including sand casting, die casting and investment casting. The quality is dependent on the process chosen. These are used for very complex geometries and usually for thicker sections. Casting are usually used in the heat treated form. Aluminum castings tend to be the most expensive product form.
Joining of alumimum can be accomplished by most traditional methods, (spot welding, MIG welding, adhesive joining, etc.) but the processing parameters MUST BE DRASTICALLY ALTERED. This has led to problems with Al in vehicles where the infrastructure for repair is not educated in these differences.
Six impressive examples of aluminum designs achieving the 40% - 50% weight reduction:
1) The bumper structure of a Buick Riviera using two aluminum extrusion and riveted assembly.
2) Underbody X members of a 98 LH rear suspension using 2 Al extrusions and two Al castings joined by arc welding.
3) Instrument Panel Support (DEW) involving an Al extrusion, Al sheet metal, and a magnesium casting
4) Windshield Surround for '97 Corvette employing Al extrusions, two Al sand castings at top corners, and 2 Al die castings at supports.
5) Prowler Frame combining mostly Al complex extrusions and a few Al castings.
6) Body in White for '92 Mercury Sable using Al sheet metal, with some Al extrusions and some Al castings, joined by spot welding, MIG welding and some quench bonding.
In all of the above cases, the Aluminum designs equalled or out-performed the traditional designs for the same function in all respects, while producing the 40% to 50% weight savings.
Economics, and service infrastructure remain the final stumbling blocks for widespread Al usage in vehicle manufacture.
In conclusion: Aluminum must be applied thoughtfully. Only a multi-product approach is cost effective. Alcoa has the breadth of experience necessary to develop such applications.