Competition Between Powder Metallurgy and Other Near Net Shape Processes: Case Studies in the Automotive and Aerospace Industries T
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Competition between Powder Metallurgy and Other Near Net Shape Processes: Case Studies in the Automotive and Aerospace Industries t Narayan V. Nallicheri Project Manager, IBIS Associates, Inc.* Joel P. Clark POSCO Professor of Materials Engineering, MIT** Introduction fabrication, and enhance material utilization With increasing industry competition, de rates, net shape and near net shape processes velopment of new alloys, stiffer price competi have been gaining in importance. These encom tion, and rising energy and material costs, there pass not only the traditional casting and forg has been a distinct trend to diverge from con ing, but also exotic powder techniques such as ventional forming technologies. The need to hot isostatic pressing, and powder forging. produce the final product in fewer processing One of the key forces driving the shift to steps with minimal material wastage has led wards near net shape production is the reduc engineers and component designers to develop tion of secondary machining or metal removal and critically evaluate alternative processing operations. The annual economic value of ma routes which would be more cost effective, terial removed, measured in terms of labor and while maintaining the same high level of per overhead, is estimated at over $125 billion in formance. Several techniques for manufacture 4 the U.S. alone ). Considering the enormous to "net shape" or "near net shape" are being economic value, it is apparent that any reduc developed to meet present and future demands. tion in metal cutting operations will provide The fundamental incentive for the develop substantial economic savings for the manufac ment of alternative fabrication processes is turing industry. To this end, there have been The reduction and, at times, elimi ~conomic. sizable efforts focused on improving the ma nation of a large number of machining steps chining operation and in developing means to provides sufficient cost savings on a per part reduce, if not eliminate, the amount of machin basis to warrant the use of net shape processes, ing required. Further, the field of machining even though they may entail extra capital has been aided by the development of a host of equipment and/or special handling equipment1). empirical relations relating the various cutting An indication of the significance of net shape parameters in order to choose the optimum processes can be found in automobile industry 5 6 cutting conditions • ) statistics: approximately fifty pounds of preci There have been a large number of changes sion formed parts are used in a typical Ameri in the field of machining itself, spurred by the can or European automobile, and about three 2 3 evolution of new materials, difficult to ma times that amount in a Japanese automobile • ). chine alloys, etc., and also by the need for The rna terial selection problem faced by pre higher precision. To meet these requirements sent day designers is also a problem of choosing there have been numerous advances in the cut the optimal processing route, especially since ting tool industry, such as the emergence of the choice of a particular material is tied to new material cutting systems and surface coat the manufacturing process employed. For ex ings aimed at enhancing tool life. Global com ample, a switch to steel from nodular iron for petition, in conjunction with the difficulty as connecting rod also implies a change in process sociated with machining some high-temperature ing from casting to forging. alloys and some composite materials, provides Driven by the need to reduce the costs of a constant incentive for the development of * 55 William St. Ste. 220, Wellesley, MA 02181, U.S.A. new tool materials and tool surface treatments ** Rm 8-409, 77 Mass. Ave., M.I.T.; Cambridge, MA 02139, aimed at extending metal removal rates. These U.S.A. advances serve to aid shifts in technology to t Received September 10, 1990. wards net shape. Figure 1 highlights the chron- KONA No.8 (1990) 105 ological order of advances in the cutting speed tinual changes in engine designs place stringent capabilities of tool materials. The improve requirements on the possible materials which ments in cutting speeds progressively achieved may be used for their manufacture. The auto over the years have been both through the motive industry, where large production vol introduction of new tool materials (solid line), umes are typical, has been an optimal environ and the use of coatings on existing tool ma ment for the penetration of these technologies. terials (dashed line). The automotive industry is one of the largest users of formed parts, either cast, forged or stamped. In 1988, the automotive industry 10000 -----·----------------------------- Polycrystalllne D1amond consumed a total of $16.9 billion worth of 0 5000 ----- -- - - -- --- -- -- --- --- --- -- -- -- D S111con steel stampings, 1.6 million tons of nodular ~ Ceramic Nitride E 1000 ----------------------------- -CompOSite iron castings, and approximately 21 lbs/auto ? 0 Ceramic u 0 Coated Carbide of metal powder?). Thus, from the point of ~ 500--------------------------- --- 0 cubic~~~3~ view of introducing new net shape processing UJ Carbide OMicroqra1n (]) 1oo ---------cast-AI-Io ____ ------;,;;;.-.:cr- carbide routes which may require high initial capital § ----- Coated HSS investments, it is preferable to have high pro (3 50------ ---·H1gh Speed Steel---· Carbon Tool Steel duction volume runs to obtain economies of 0+------r----~------~-----, scale, which are typical of the automotive in 1800 1850 1900 1950 2000 Year dustry. In the case of P/M, almost 70% of the end of metal powder can be traced to the auto motive industry8>. Further, as mentioned above, Fig. 1 Chronological development of tools with the automotive industry is under continuous their cutting speed capability pressure to innovate and use lighter, stronger materials for its components. Figure 2 presents The technologies summarized above are just the trend of iron powder shipments used solely 9 a tip of the iceberg as far as the whole range of for P/M parts ). The increasing trend clearly possible fabrication routes available for metals shows the enhanced used of P /M parts in auto processing are concerned. There is an interde mobiles. In fact, General Motors recently an pendence between the technologies themselves, nounced their intention to use at least 18-20 to a limited extent, and between the primary lbs of powder parts per automobile in the next 10 fabrication routes and secondary routes, such few years ). as machining, to a larger extent. Although part The advent of new materials and near net of this shift towards near net shape technologies technologies is not limited to the automotive is material driven, a large fraction still stems industry alone. Table I tabulates the projected from the economic advantages to be reaped by growth rate for RS materials in the U.S. The a shift in technology. The advent of these new growth of these exotic materials is tied into the technologies warrants active markets where growth of the near net technologies associated 11 possible applications can be found. The range with their processing ). of applicability depends on the level of eco From the foregoing discussion it is apparent nomic savings offered by near net shape tech that there is currently a great deal of interest nologies, and on the performance characteris in the advent of near net shape technologies. tics obtainable. Further, a particular applica The prime motivation for a shift in technology tion may, at times, warrant the use of a high towards net shape is economic, though per performance material due to performance re formance considerations are also of importance. quirements. A change in material may also be The above discussion also suggests that there is associated with a change in processing route. a dual nature to the materials selection prob Thus competition between technologies may lem. Designers need to lay emphasis not only arise out of pure performance considerations on the level of performance delivered by the based on the limitations of the current material/ component, but also on the costs of manufac process. ture. The scenario outlined above is quite preva The drive towards more powerful, fuel effi lent in the automotive industry where con- cient aerospace engines has been such that, 106 KONA No.8 (1990) 200 --------------------------------------------- ever, the next decade will show an increasing 180 ------------------------------ -- - - --- -- """' -- competitiveness among consortia as designers, 160-------- builders, and marketeers of engines. <J) § 140 Currently, about 91% of the weight of an f- a 120 advanced gas turbine engine consists of either ~ 100 1-·· superalloys (41.5% ), steel (26.5% ), or titanium c iJi 80 ::; (23.5%), with the balance being made up of _g 60 f- aluminum and small amounts of magnesium, 40 polymers/polymer matrix composites, and re 20 --m:- ,__ _ fractory materials. Superalloys are expected to 0 maintain their superiority in this market, and 1976 1978 1980 1982 1984 1986 1988 by 1998 the mix of materials used is expected Fig. 2 Iron powder shipments for P/M parts to become 43% superalloys, 23.5% steel, and 22.5% titanium ts). A breakdown of the overall materials consumption is presented in Table 3, Table 1 Projected growth for RS materials in the U.S. 11) and in Fig. 3. This attractive market potential for super Average, Annual $ (millions) alloy materials makes it an active area of re growth rate % 1988 1993 search, especially when considering the prolif Metallic glasses 52* 10.0** 81.0** eration of gas turbine applications. The attrac Iron base alloys 10 62.0** 100.0** tive high temperature properties offered by this Superalloys 7 54.0 76.0 Aluminum alloys 22 3.0 8.0 class of materials makes it the obvious choice Titanium alloys 20 0.2 0.5 for certain applications. The traditional process Ceramics 68 0.15 2.0 ing routes, casting and forging, are being re -·····-·····------------------- *-New technology, starting from small base placed by powder metallurgical routes.