AMMTIAC Quarterly, Vol. 2, No. 1 - Advanced Materials ...

Named after the Titans in Greek mythology, the element titanium hasbeen known to exist since the late 18th Century. The technologicaldevelopment and application of the metal and its alloys, however, haveonly been making significant advancements in the US since the end ofWorld War II. For the past 60 years or so, US industry, academia andgovernment have been engaged in efforts to unravel the refining and fabricationproblems posed by this metal, whichholds several promising properties and characteristics.Processing titanium was a particular challenge,partly because the metal becomes verychemically active at elevated temperatures. Oneof the more notable achievements in the advancementof titanium fabrication technology was thedevelopment of rammed graphite casting. Thiscasting process, which is the subject of the featurearticle in this issue, has been in use for more thanhalf a century.The properties of titanium remained somewhatof a mystery into the early part of the 1900s. Forexample, it was initially believed to have a meltingpoint greater than 6000°F. The General ElectricCompany looked into using the pure metal formfor lamp filaments to replace carbon. This pursuitwas dropped when it was determined that theactual melting point of nearly pure titanium was approximately 3000°F,and the company settled on tungsten instead. In addition, there were severalattempts to develop a large scale process for reducing pure titaniumfrom its naturally occurring ore form. It took until the middle part of the20th Century before a commercial scale process was developed for producingraw titanium stock. By the mid-1950s titanium production grewto significant levels. Ever since, the production of titanium has been dictatedby the demands of the aerospace and defense industries, which cyclethrough highs and lows. The significant technological advancements forthe metal and its alloys have also traditionally been driven by the aerospaceand defense industries.This past spring I came across a historical relic that was very influentialin the development of titanium technology. At the conclusion ofthe Aging Aircraft Conference in Palm Springs, California, I drove toPalmdale to visit my brother and sister-in-law. (Palmdale is a small city inAntelope Valley, which is on the western edge of the Mojave Desert andthe home of Lockheed Martin’s famous Skunk Works ® *.) While theremy brother and I went to Blackbird Airpark, a relatively small, outdooraircraft museum that is now the home of a few very historicaircraft. Among the notable aircraft on display was the A-12 #60-6924,the first A-12 ever flown. The A-12 aircraft (the original Blackbird andpredecessor of the more famous SR-71) was developed in the late 1950sand early 1960s for the Central Intelligence Agency (CIA) under a highlysecret program, Project OXCART; it was designed as a potential replacementfor the U-2, a high-altitude reconnaissance aircraft.A Brief Historyof Titanium(Metal of the Titans)The A-12 #60-6924 – the Original Blackbirdand First Titanium Aircraft – Locatedat Blackbird Airpark in Palmdale, CA.The design and material selection for the A-12 was daunting due to thesupersonic and high altitude performance requirements. The aircraftskin, for instance, would be subjected to high temperatures, which precludedmost common aircraft metals from use. The one metal that couldbring their design concept to reality was titanium, even though there wereseveral technological advancements that would need to occur first. Ultimately,a beta titanium alloy, which had a greatstrength-to-weight ratio and good resistance tohigh temperatures, was selected. Practically theentire aircraft was made from titanium. Machiningof titanium was also especially difficult, and newtooling was developed for the explicit purpose offabricating titanium parts for the A-12.Even though the program was highly secret,President Johnson acknowledged that the US hadbeen engaged in an effort to develop an advancedjet aircraft. (He did intentionally mention the nameof an earlier design, the A-11, rather than identifythe existence of the A-12.) The President also notedduring his public announcement that a “mastery ofthe metallurgy and fabrication of titanium metal”had been achieved to help make the program a success.In this case, the need for an advanced aircraftdesign pushed the technological development oftitanium metallurgy and manufacturing processes, ultimately resulting inthe A-12 – the first aircraft built out of titanium. Its famed successor, theSR-71, was also built out of titanium.The history of advancements and applications of titanium technologyis interesting, especially the era between the late 1940s and early 1960s,and much of this history has been preserved. AMMTIAC is a centerthat is the culmination of numerous predecessors, the most notable ofwhich was the first: the Titanium Metallurgical Laboratory, established in1955. Much of the history of the development titanium, therefore, hasbeen preserved in AMMTIAC’s library. If you’re interested in any legacyor current information on titanium, do not hesitate to contact me. Andif you’re ever in the Palmdale area, I highly recommend making a stop atBlackbird Airpark.Ben CraigEditorGENERAL REFERENCES AND NOTE:“Titanium Progress to Date,” Titanium Metallurgical Laboratory, March 25, 1957.D. Eylon and S.R. Seagle, “Advances in Titanium Technology – an Overview,”Science and Technology of Light Metals in the 21st Century, Journal of the JapanInstitute of Light Metals, Vol. 50, No. 8, 2000, pp. 359-370.T.P. McIninch, “The Oxcart Story – Record of a Pioneering Achievement,” CIAHistorical Review Program, Central Intelligence Agency, 1994. (Approved forRelease)* Skunk Works is a registered trademark of the Lockheed Martin Corporation.Editor-in-ChiefBenjamin D. CraigPublication DesignCynthia LongTamara R. GrossmanInformation ProcessingPatricia BissonettePerry OnderdonkInquiry ServicesRichard A. LaneProduct SalesGina NashThe AMMTIAC Quarterly is published by the Advanced Materials, Manufacturing, and Testing InformationAnalysis Center (AMMTIAC). AMMTIAC is a DoD-sponsored Information Analysis Center, administrativelymanaged by the Defense Technical Information Center (DTIC). Policy oversight is provided by the Office of theSecretary of Defense, Director of Defense Research and Engineering (DDR&E). The AMMTIAC Quarterly isdistributed to more than 18,000 materials, manufacturing, and testing professionals around the world.Inquiries about AMMTIAC capabilities, products, and services may be addressed toMicheal J. MorganDirector, AMMTIAC937.542.9908EMAIL: ammtiac@alionscience.comURL: http://ammtiac.alionscience.comWe welcome your input! To submit your related articles, photos, notices, or ideas for future issues, please contact:AMMTIACATTN: BENJAMIN D. CRAIG201 Mill StreetRome, New York 13440PHONE: 315.339.7019FAX: 315.339.7107EMAIL:ammtiac@alionscience.com

Stephanie O’ConnorATI Wah Chang, an Allegheny Technologies CompanyAlbany, ORINTRODUCTIONDesign engineers are faced with multiple considerations when itcomes to component design and fabrication for military applications,including ease of assembly, weight reduction, structuralintegrity, corrosion resistance, long term maintenance costs, andoverall affordability. These considerations often conflict as designengineers begin to weigh the costs and benefits of each option.In the quest to achieve the best cost/benefit scenario, oldertechnologies can get overlooked in favor of newer technologies. Aprime example of an older technology that can meet today’s needsis titanium rammed graphite castings for military applications.HISTORYTitanium rammed graphite castings have been used for commercialand military applications since the late 1950s. Originally, thecast titanium parts were desired because of their superior performancein severe service applications like seawater, but designengineers quickly discovered that other benefits could also berealized by utilizing cast parts. A primary benefit was the abilityto produce near net shapes that required less material, lessmachining, and reduced scrap. Titanium’s weight advantagecompared to steel also became an advantageous characteristic.Over the last 50 years, titanium rammed graphite castingshave been used for multiple military applications, such as firepumps, water pumps, condenser head covers, and hose-to-hosepipe connectors on surface ships, torpedo ejection pumps, largeseawater pumps, various sizes of ball, gate and butterfly valves,and other defense components. Figures 1 and 2 show examplesof four different titanium components made using the rammedgraphite casting process.THE PROCESSPatterns and MoldsTitanium rammed graphite castings are made using wood, metal orplastic patterns to produce a mold, as illustrated in Figure 3. Similarto conventional sand castings (see sidebar), rammed graphite castingsuse the standard cope and drag patterns, with and without cores.Many parts can be cast using the same patterns originally constructedfor the casting of other metals. Standard loose or match-platepatterns made of either wood or metal can be used for titaniumrammed graphite castings. Standard core boxes can also be usedunless they are designed to be used for core blowing only. Most patternsfor ferrous and nickel-based alloys will conform dimensionally.Pattern shops can accommodate modifications or new construction.Generally, pattern equipment designed for sand casting processes canalso be utilized with modifications to gating and riser systems.Titanium is very reactive in the molten state, and thereforegraphite is used as a mold medium. Graphite powder is mixedwith water, pitch syrup, and starch, which act as binders. Thismixture is pneumatically tamped and rammed around the patternto form the mold.Figure 1. Cast Titanium Pump Casing (Left) and a Cast TitaniumSeal Head (Right).http://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 3

Table 1. Chemical Compositions of Various Grades of Titanium.Chemical Composition, max wt.%ASTM Designation Ti (min) C H O N Fe OthersGrade 2 98.885 0.10 0.015 0.25 0.03 0.30 0.30Grade 3 98.885 0.10 0.015 0.35 0.05 0.30 0.30Grade 5 Remainder 0.10 0.015 0.20 0.05 0.30 6.75 Al, 4.50 VGrade 7 99.005 0.10 0.015 0.25 0.03 0.30 0.12-0.25 PdGrade 12 Remainder 0.10 0.015 0.25 0.03 0.30 0.2-0.4 Mo, 0.6-0.9 NiGrade 38 Remainder 0.00 0.00 0.25 0.00 1.50 4 Al, 2.5 VCHARACTERISTICS OF CAST TITANIUMIn Corrosive EnvironmentsThe majority of titanium alloys (wrought or cast) are very resistantto corrosive attack and virtually immune to many oxidizing andreducing environments. This is due primarily to a tenacious oxidefilm that is formed when titanium is exposed to the atmosphere.The oxide film acts as a barrier to the surrounding corrosive environmentand thereby protects the titanium alloy from furtheroxidation and corrosion. By combining titanium with smallamounts of palladium or molybdenum and nickel, the corrosionresistant properties of the titanium alloy can be improved further.Strength and Structural IntegrityUnlike aluminum and steel alloys, which tend to lose structuralintegrity and strength when cast, titanium tends to maintainstructural integrity and strength that is comparable to wroughttitanium products. Table 2 illustrates this point by comparingtensile and yield minimums for wrought and cast titanium alloyscommonly used in chemical processing and defense applications.Dimensional Control of Titanium Rammed Graphite CastingsRammed graphite castings made with titanium alloys are eitherstatic or centrifugally cast, depending on the shape and size ofthe cast part. Common tolerances for titanium rammedgraphite castings are listed below; tighter tolerances can beachieved with additional trials and correction efforts:• Minimum Section Thickness: 3/16", 1/8" if less than onesquare inch of surface• Base Tolerance:• Up to one linear inch: ± 1/32"• 1 inch up to 10 inches: ± 1/16"• 10 inches up to 20 inches: ± 1/8"• 20 inches up to 60 inches: ± 3/16"• Additional Tolerances:• For dimensions across the parting line: ± 1/8"• Added tolerance for dimensions affected by parting line andparallel to the parting line (mismatch):• Less than 10 inches: ± 1/16"• 10 inches and above: ± 1/8"• Radius Dimensions:• General radius conforms to base dimensions• Sharp to 1/8" radius ± 1/32" (convex)• Up to 1/2" fillet radius ± 1/32" (concave)• Finish Stock:• Nominal 1/8" on all machined surfaces on dimensions lessthan 12"• Nominal 3/16" – 1/4" on all machined surfaces greaterthan 12"• Angles: ± 1 degreeThe Basicsof MetalCastingBenjamin D. CraigAMMTIACRome, NYCasting is a manufacturing process that has been in use for several millennia; cast metals, for example, have beendated back to 4000 B.C. There have been advancements in the process over the years, but the basic principles haveremained. A molten or liquid material (either a metal, polymer, or ceramic) is poured into a mold, where it conformsto the shape of the cavity, and then is solidified to create a finished or nearly finished product. The processis often used to efficiently form complex parts and is typically a cheaper route compared to the alternativefabrication methods, such as forming or machining from a solid. The size of the castings can range from hand heldpieces (and smaller) to multi-ton items such as ship propellers.A pattern is the three dimensional model that is designed and used to create a mold cavity, which will ultimatelyform the final casting product. Patterns can be reusable or expendable. The reusable patterns are typically made fromwood, metal, plastic, or a composite material and can be used to make duplicate molds. Expendable patterns, on theother hand, are made of materials such as wax, polystyrene, or other plastics and are disposed of after making themold. In the case of the lost Styrofoam ® method, the pattern is vaporized during casting process.*Traditionally, the molds for casting metals have been made with prepared sand (called green sand casting becauseit is unfired), although other materials can be used. Typically these mold materials include a binding material (clay)and a small percentage of water so that after molding the sand retains the exact inverse of the pattern shape. Theprepared sand retains an imprint of the pattern to create the casting cavity that will eventually host the moltenmetal. A common practice of casting metals is to create the mold in two parts. The top part of a mold is calledthe cope and the bottom part is called the drag. These two components are separated at what is referred to as aparting line. Molds are held in place and supported during the casting process using a frame called a flask, whichis typically made of wood or metal. A core is a separate solid material within the mold cavity that is used to makean internal void or passageway in the final product. The pattern is modified to allow for the positioning and retentionof the core in an exact location. Figure 1 illustrates some of the common components of a mold.* Styrofoam is a registered trademark of the Dow Chemical Company.6The AMMTIAC Quarterly, Volume 2, Number 1

Table 2. Comparison of Strength Specifications for Cast andWrought Forms of Various Grades of Titanium [1], [2].Titanium Grade Tensile Strength, min. Yield Strength0.2% Offset, min.Ksi MPa Ksi MPaCast Grade 2 50 345 40 275Wrought Grade 2 50 345 40 275Cast Grade 3 65 450 55 380Wrought Grade 3 65 450 55 380Cast Grade 5 130 895 120 825Wrought Grade 5 130 895 120 828Cast Grade 38 130 895 115 794Wrought Grade 38 130 895 115 794Size and WeightsWhile the size and weight of titanium rammed graphite castingscan vary depending on the manufacturer, 1 to 1300 pounds is acommon weight range for cast titanium alloys. Larger castingscan be produced by fabricating several castings into a singlecomponent. In certain configurations, casting weights in excessof 1300 pounds are possible but they should be evaluated on acase by case basis.CONCLUSIONWhile titanium rammed graphite castings are not new to themilitary, they are often overlooked as an alternative to traditionalmanufacturing processes and wrought products utilized inthe production of defense components. Today, design engineerscan realize many military objectives by utilizing titaniumrammed graphite castings to ease the burden of assembly, reducecomponent weight, maintain structural integrity, increasecorrosion resistance, cut back lead times and reduce long termmaintenance costs. While titanium rammed graphite castingsmay not be the newest technology available, it certainly could bethe best choice – especially when weighed against the militaryobjectives of today and tomorrow.NOTE AND REFERENCES* Melt stock raw materials are more readily available than mill productsbecause mill products must be manufactured from the ground up,whereas melt stock raw materials can be taken from mill products thathave already been produced and are in the inventory.[1] “ASTM Designation B 367 – 06,” Standard Specification forTitanium and Titanium Alloy Castings, ASTM.[2] “ASTM Designation B 265 – 06b,” Standard Specification forTitanium and Titanium Alloy Strip, Sheet, and Plate, ASTM.GENERAL REFERENCESM. Guclu, I. Ucok, and J.R. Pickens, “Effect of Oxygen Content onProperties of Cast Alloy Ti-6Al-4V,” Symposium on Cost-AffordableTitanium, Charlotte, NC, March 2004, The Minerals, Metals &Materials Society, Inc., pp. 135-143, DTIC Doc.: AD-P016696.D. Eylon, F.H. Froes, and L. Levin, “Effect of Hot Isostatic Pressingand Heat Treatment on Fatigue Properties of Ti-6Al-4V Castings,”Proceedings of the Fifth International Conference on Titanium, 1985,pp. 179-186, DTIC Doc.: AD-D135659.R.D. Williams and J. Dippel, “Comparisons of Titanium Investmentand Rammed Graphite Castings,” Titanium Net Shape Technologies,The Metallurgical Society of AIME, 1984, pp. 193-199, DTIC Doc.:AD-D134602.More Titanium Rammed Graphite Castings reports available throughPrivate STINET and TEMS. Qualified users can access these databasesthrough the DDR&E Research Portal (https://rdte.osd.mil/).The mold cavity in the cope and drag can be formed using different types of patterns, such as a standard loosepattern or a match plate pattern. The match plate has a pattern mounted on both sides of the pattern plate andconforms to the parting line between the cope and the drag parts of the mold. The match plate system typicallyuses an interlocking feature that surrounds the exterior edge ofthe pattern. This ensures a very accurate registration of the moldhalves and restricts movement of the mold during solidificationof the metal.During the casting process, shrinkage of the casting material canoccur during solidification. To account for this, risers are usedwhich act as a molten metal reservoir to fill any voids created whenthe casting shrinks inside the mold cavity. Risers that do not havean outlet on the topside of a cope are called blind risers. Vents areused to allow for gases to escape in order to reduce the occurrenceof voids in the casting. A sprue is the vertical channel in the moldthat connects the pouring basin to the gating system. Some moldsdo not have a pouring basin, in which case the molten metal ispoured directly into the sprue. The gating system is a series of passagewaysthat distributes the molten metal between the sprue andthe casting cavity. Design of a proper gating system is importantbecause it allows the liquid to flow and enter the casting cavity properly in order to avoid defects in the final casting.The use of so called green (unfired) or fused sand allows for the easy removal of the sand from the solidifiedmaterial. Additionally, the sand can be reprocessed, and when clay and water are added it can be used for the nextseries of castings.PartingLineFlaskSpruePouring BasinGating SystemBlind RiserCompacted Green SandVent HoleFigure 1. Components in a Green Sand Casting Mold.CopeCoreMoldCavityDraghttp://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 7

Calendar of EventsSeptember 2007Corrosion Solutions 20076th International Conference9-13 September 2007Sunriver, ORFor additional information:www.csc07.com/index.phpMS&T ‘07 (Materials Science & Technology2007 Conference and Exhibition)16-20 September 2007Detroit, MIFor additional information:www.matscitech.org24th Annual ASM Heat Treating Society Conferenceand Exposition17-19 September 2007Detroit, MIFor additional information:www.asminternational.org/heattreat2007 SAE AeroTech Congress& Exhibition17-20 September 2007Los Angeles, CAFor additional information:www.sae.org/aerotech9th Fleet Maintenance Symposium 200718-19 September 2007Virginia Beach, VAFor additional information: www.asne-tw.orgMaterials Processes & MedicalDevices Conference23-25 September 2007Palm Desert, CAFor additional information:www.asminternational.org/meddevices/October 200715th Annual SMRP Conference7-10 October 2007Louisville, KYFor additional information:www.smrp.org/default.aspCold Spray Conference8-9 October 2007Akron, OHFor additional information:www.asminternational.org/coldspray/website/default.htmInternational Symposium on Advancesin Surface Hardening of Stainless Steels22-23 October 2007Cleveland, OHFor additional information:www.asminternational.org/surface/website/default.htmDiminishing Manufacturing Sources and MaterialShortages 2007 (DMSMS 2007)29 October – 1 November 2007Orlando, FLFor additional information:www.dmsms2007.comNovember 200733rd International Symposium for Testing andFailure Analysis4-8 November 2007San Jose, CAFor additional information:www.istfa.orgCommercialization of NanoMaterials 200711-13 November 2007Pittsburgh, PAFor additional information:www.tms.org/Meetings/specialty/nano07/home.html55th Defense Working Group on Nondestructive Testing13-15 November 2007Ft. Walton Beach, FLFor additional information:http://hometown.aol.com/dodndtIMAPS 200711-15 November 2007San Jose, CAFor additional information:www.imaps.org/imaps 2007DoD Maintenance Symposium& Exhibition13-16 November 2007Orlando, FLFor additional information:www.sae.org/events/dod/Advanced Materials and Manufacturing Technologyfor Naval Applications Conference14-15 November 2007Baltimore, MDFor additional information:www.nmc.ctc.com/index.cfm?fuseaction=eventinfo&id=45National Nano Engineering Conference (NNEC 2007)14-15 November 2007Boston, MAFor additional information:http://nasatech.com/nano/December 2007Tri-Service 2007 Corrosion Conference3-7 December 2007Denver, COFor additional information:www.nace.org/nace/content/conferences/triservice07/8The AMMTIAC Quarterly, Volume 2, Number 1

techsolutions 4John C. KeefeAlion Science and TechnologyRome, NYA Brief Introduction to Precious MetalsINTRODUCTIONA precious metal (PM) can be defined as a rare metallicchemical element of high economic value.[1] Preciousmetals, as a group, have a set of physical and chemicalproperties that are unrivaled by many other materials. Ifthe availability of these materials was greater (in bothquantitative and economic terms), there would be far moreapplication overall. Due to the cost and availability,however, these materials are limited to applications whereonly small amounts are used, such as spark plug tips andelectrical contact plating. Under certain circumstances,precious metals are used in large quantities for applicationswhere there is no feasible substitute. In applications andindustries that use a large amount of PM, the capital costcan be great (tens of millions of dollars), and there is also asubstantial cost associated with managing and securing themetal assets in a company’s inventory.The Eight Precious MetalsThere are eight precious metals: gold (Au), silver (Ag),platinum (Pt), iridium (Ir), palladium (Pd), rhodium (Rh),ruthenium (Ru), and osmium (Os). They are grouped in arectangle on the periodic table existing in two periods andfour groups. A subset of this group is called the PlatinumGroup Metals (PGM), which includes all but two of thePMs (Au and Ag).Mining the Raw MaterialsTypically the PGMs are found combined together in rich oreand are then chemically processed to extract the individualelements in the group. Also notable are the elements abovethe precious metal group on the periodic table: iron (Fe),cobalt (Co), nickel (Ni) and copper (Cu). All of these metalshave relationships with the eight precious metals, in thatthey are found in the primary ore, or they are used asalloying elements to impart improved properties in manyof the precious metal formulations. The short supply (thereare only a few major mining locations), economic valueand costly mining and extraction methods have raised thecost of these metals to the high prices that exist today.Gold and silver have been in use for a very long time,but the other precious metals have a much shorter history.The discovery of PGMs occurred significantly later sincethey are not typically available in the pure metal nuggetform in which gold and silver are found. Mining locationsfor the PGMs are very limited. The key areas of PGMproduction are the US (Stillwater, Montana), Canada (mostcommonly the Sudbury, Ontario area, as a byproduct ofnickel mining), Russia (Norilsk region, which is first in Pdproduction), and the Zimbabwe region in South Africa (firstin Pt and first in PGM general production). In 2004, SouthAfrica produced a total of five million troy ounces (to)* ofPt (70% of the world’s output) and eight million troyounces of PGMs (50% of the world’s output).[2] Today theprocessing of PGMs requires about a ton of rich ore toproduce approximately one troy ounce of PGMs at best.Some mines only produce PGMs on the level of 5 to 25grams per ton of processed ore. Whereas PGMs are mined infewer locations, the occurrence of gold and silver is muchmore common and they are found in larger quantities.BASIC PROPERTIES OF PRECIOUS METALSThe properties of PMs are typically different than conventionalmetals in two primary areas: melting point (MP) anddensity. The melting point for steel (low alloy iron) is in therange of 2800°F with a density in the range of 7.8 g/cm 3 ;compare this to the group to see the differences on thephysical property side. These features, coupled with theirresistance to chemical attack, set PMs apart from most otherTable 1. Basic Properties of Precious Metals.Name (Symbol) Atomic Crystal Melting Density,Number Structure Point, °F g/cm 3Ruthenium (Ru) 44 HCP † 4190 12.45Rhodium (Rh) 45 FCC ‡ 3560 12.41Palladium (Pd) 46 FCC 2829 12.02Silver (Ag) 47 FCC 1764 10.49Osmium (Os) 76 HCP 5522 22.61Iridium (Ir) 77 FCC 4429 22.65Platinum (Pt) 78 FCC 3216 21.45Gold (Au) 79 FCC 1947 19.32http://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 19

techsolutions 4Table 2. Mechanical Properties of Precious Metals [3,4].Name Tensile Strength Elongation in Hardness Young’s Modulus (Static) Poisson’s Ratio(MPa) 50 mm (%) (HV) at 70°F (GPa)Ruthenium 496 3 220-270 414 0.25-0.31Rhodium 1379-1586 2 13-100 319 0.26Palladium 324-414 1.5-2.5 105-110 115 0.39Silver 290 3-5 25 74 0.37Osmium - - 31-350 558 0.25-0.28Iridium 2070-2480 15-18 600-700 517 0.26Platinum 207-241 1-3 90-95 171 0.39Gold 207-221 4 55-60 77 0.42Table 3. Electrical Resistivity and Thermal Conductivity of PMsCompared to Copper and Aluminum [5].Metal Electrical Resistivity Thermal Conductivity(10 -6 ohm-cm) (W/m-K)Silver 1.55 419.0Copper 1.70 385.0Gold 2.20 301.0Aluminum 2.70 210.0Rhodium 4.30 151.0Iridium 4.70 147.0Ruthenium 7.20 116.0Osmium 8.12 91.67Palladium 9.93 71.20Platinum 10.6 69.10materials on the periodic table.[3] Table 1 shows some ofthe basic properties of the eight precious metals. Severalmechanical properties of the PMs are providedin Table 2.Electrical and Thermal ConductivityMany of the PMs have excellent electrical and thermalconductivity properties, as shown in Table 3. Silver has thedistinction of having the highest room temperatureconductivity of the PMs, as well as the highest of allmetals. It should be no surprise that copper is the metalmore predominantly used for electrical wire instead ofAg because of the cost difference. The main drawback toCu is that it readily forms an oxide film, which can lowerthe electrical properties unless the oxide film is cleanedfrom the electrical contacts. This problem is commonlyresolved by plating the contact area of Cu electricaldevices with gold.NobilityThe precious metals are often called the “Noble Metals”because they are resistant to most types of environmentaland chemical attack. One of the few chemical solutions toattack the precious metals (with the exception of iridium)is aqua regia (Latin for “royal water”). Aqua regia, amixture of one part nitric acid (HNO 3 ) with three partsof hydrochloric acid (HCl), earned its name because itdissolves Au and Pt, the royal or noble metals. Thissolution is used as an etching solution for metallurgicalanalysis of many metals.APPLICATIONSAs with most materials, the range of applications for PMsis diverse. However, PM materials are also used inapplications where other materials cannot be used. Thefollowing sections provide an overview of typical PMapplications.Corrosion ProtectionThe use of PMs to resist corrosion is long-standing due totheir inherent nobility. Additionally, these metals and theiralloys are used in cathodic protection systems to protectlarge systems from the effects of corrosion.CatalystsThe use of Pt, Pd, Rh and their various alloys as catalystsin large and small chemical reactors, such as car exhausts,is widespread. The catalytic surface can be applied by“washing on” a rich solution of material onto a ceramicsubstrate. The surface can also be a robust construction ofwoven wire in order to provide a large-scale surface forchemical production. These applications account for theprimary usage of PMs. Platinum-based catalysts have beenused for nitric acid production for more than 100 years.High Temperature ApplicationsCombining high MP temperatures with the additionalfeature of low reactivity at elevated temperatures is a keycharacteristic of PMs for many applications. Steel melts atapproximately 2800°F, while Pt has a MP of 3200°F.Vessels made from Pt, Pt-Rh, and Ir are used in the makingof fiberglass and silicon ingots, as well as for the meltingof other high MP, reactive media. One clever applicationuses Pt and zirconium oxide to form a powdered metalthat is a highly creep resistant material even when heatedclose to its melting point. Zirconia Grain Stabilized (ZGS)platinum and Pt-Rh alloys have been used in the glass10The AMMTIAC Quarterly, Volume 2, Number 1

A DVANCED M ATERIALS, MANUFACTURING AND T ESTINGAMMTIACindustry for many years. The addition of zirconium and itssubsequent oxidation during metal spraying create a grainstructure that limits grain growth and increases the hightemperature creep strength.Thermocouple DevicesPlatinum and platinum-rhodium wire pairs for thermocouplesare the most effective at measuring temperature.Platinum thermocouples exhibit the widest range oftemperature measurement, accuracy and linearity, whichis required for critical applications. Currently, the producersof wire are able to make wire diameters small enough thatthe cost of PM material is kept to a minimum.High Temperature Heating CoilsA heating coil can obviously only go as high as the meltingpoint of the material used to construct the device. Additionally,in many operations repeated oxidation cycles can reducethe life of the heating coil. The use of PGM alloys satisfiesboth the issue of high service temperature and the problemof long-term oxidation attack.Spark Erosion Resistance ApplicationsIn the new generation of cars and trucks, replacing sparkplugs could be a thing of the past. The developmentand application of Pt alloys, Ir alloys, and pure Ir (somecombinations of PMs are patented) make plugs thatlast for more than 100,000 miles. To accomplish this, somemanufacturers use ball bearing fabrication equipment tomake small Pt alloy spheres that are then resistance weldedonto the plug to form the electrode pair. For the morecritical applications on aircraft, short pieces of Ir rod stockmaterial are centerlessly ground § to an exacting size andform and then installed in the spark plug. Additionally,electrical contacts with an extended operational lifecapability have been made from Pt and Pd strip stockfor various devices by high speed stamping of smallcrowned circular blanks.Fuel Cell ApplicationsFuel cells are similar to conventional batteries in that theyare silent with no moving parts and generate electricalpower by an electrochemical reaction within the cell. Thebest part about a fuel cell, unlike a battery, is that itrequires no recharging and it will run continuously as longas the fuel supply lasts. The electrical output from thefuel cell is made by combining hydrogen (the fuel) andoxygen (from air) over a catalyst such as platinum.BiocompatibilityNot all materials have the ability to be implanted within orused in contact with the human body without causing anadverse reaction or poisoning. Those that can be are termedbiocompatible. The medical devices produced from PMsinclude: stents, marker bands for angioplasty devices,pacemaker wire, heart muscle screw fixations, endoscopytips and special surgical tools. The material used for suchapplications is mainly Pt (or alloys of Pt), and in dentalapplications the use of Au and Pd is common.Radio-opacityX-rays do not easily pass through Pt, Au and Ir becauseof their atomic absorption coefficients, as well as their highdensities, and thus these materials typically show up as awhite area on film or scanning device. This property,referred to as radio-opacity, coupled with their biocompatibilitycharacteristics allows for the location of thesematerials to be determined when used within the humanbody. The identified location of these materials is called the“marker band” because it marks the location to allow thesurgeon to correctly position the angioplasty device withinthe body during surgical procedures.Pharmaceutical UsePlatinum-based drugs, such as cisplatin, have been in usefor 30 years to treat cancer. The treatment of testicularcancer with cisplatin has been widely accepted as a standardcourse of treatment. A new drug, stataplatin, is under thelast stages of FDA approval for treatment of a form ofprostate cancer. This new drug will offer an alternative tothose patients that did not respond well to chemotherapy.Gold has also been used for the treatment of prostatecancer, whereby small gold “seeds” are irradiatedand injected into the cancer site to kill the cancer cellsby the slow release of radiation.Labware, Equipment & Related DevicesPlatinum and gold have an excellent resistance to attackfrom many substances, and as such they are used ascrucibles, electrodes, inoculating loops, ignition boats andmany other forms of labware. Since these materials arenoble, the testing method is not skewed by contaminationfrom the test equipment. Basic forms of material (wire, tube,sheet, and strip) can be fabricated into countless products asrequired for industrial use. Joaquim Bishop, a former labassistant at the University of Pennsylvania, established thefirst Pt works in the US in 1842 for the purpose of refiningPt and the production of Pt labware. His early success inthis work earned him a prestigious Franklin Institute silvermedal in 1845 for “skill and ingenuity in the manufacture ofPt scientific instruments.” Many of the complex Pt alloyfabrications have been used in the production of glassmelting “bushings” for the fiberglass industry.[6]Photographic ApplicationsPhotography’s impact on society has been vastly importantover the last 150-plus years since its discovery. During theformative period of discovery, precious metals played a keyrole in making the art a reality. At one time, the EastmanKodak Company was the single largest user of silver in theworld. Many films and photo papers used silver compoundsas the light-sensitive emulsion. Platinum and palladiumcompounds were used to make black and white printingpaper, which was and still is considered by many to be thebest paper for reproduction of the complex tonality on blackand white negatives. These prints are the most archived ofany produced because of their resistance to environmentalattack. Famed photographer Ansel Adams used gold chloridehttp://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 11

AMMTIAC DirectoryTECHNICAL MANAGER/CORDr. Lewis E. Sloter IIAssociate Director, Materials & StructuresODUSD(S&T)/Weapons Systems1777 North Kent Street, Ste 9030Arlington, VA 22209-2110703.588.7400, Fax: 703.696.2230Email: lewis.sloter@osd.milDEFENSE TECHNICAL INFORMATION CENTER(DTIC) POCMelinda Rozga, DTIC-I8725 John J. Kingman Road, Ste 0944Ft. Belvoir, VA 22060-6218703.767.9122, Fax: 703.767.9119Email: mrozga@dtic.milAMMTIAC DIRECTORMicheal J. Morgan201 Mill StreetRome, NY 13440-6916937.542.9908, Fax: 315.339.7107Email: mmorgan@alionscience.comAMMTIAC DEPUTY DIRECTORChristian E. Grethlein, P.E.201 Mill StreetRome, NY 13440-6916315.339.7009, Fax: 315.339.7107Email: cgrethlein@alionscience.comMATERIALS TECHNICAL DIRECTORJeffrey D. Guthrie201 Mill StreetRome, NY 13440-6916315.339.7058, Fax: 315.339.7107Email: jguthrie@alionscience.comCONTRACTS MANAGERDavid J. Brumbaugh201 Mill StreetRome, NY 13440-6916315.339.7113, Fax: 315.339.7107Email: dbrumbaugh@alionscience.comMANUFACTURING TECHNICAL DIRECTORChristian E. Grethlein, P.E.201 Mill StreetRome, NY 13440-6916315.339.7009, Fax: 315.339.7107Email: cgrethlein@alionscience.comTECHNICAL INQUIRY SERVICES MANAGERRichard A. Lane201 Mill StreetRome, NY 13440-6916315.339.7097, Fax: 315.339.7107Email: rlane@alionscience.comNON-DESTRUCTIVE EVALUATIONAND TESTING TECHNICAL DIRECTORDr. George A. Matzkanin3096 Stevens Circle SouthErie, CO 80516303.774.0651, Fax: 303.774-0652Email: gmatzkanin@tri-austin.comHelp us improve the quality of our publication!http://ammtiac.alionscience.com/aqsurveyAMMTIACanswers materials, manufacturing,and testing questionsCALL: 315.339.7090EMAIL:ammtiac@alionscience.comORVISIT:http://ammtiac.alionscience.com/expertshttp://ammtiac.alionscience.com The AMMTIAC Quarterly, Volume 2, Number 1 15

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