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Appendix A HIP Casting Consolidation Technology Hot isostatic pressing (HIP) is a generic name for materials processing at high temperature and pressure. The earliest applications of HIP include powder metallurgy and consolidation of carbides. This study examines the development and diffusion of the concept of HIP casting: hot isostatic pressing for the purpose of closing porosity in castings. The following technical and market structure conditions underlie the technology transfer process. Techn ical Conditions 1. Alcoa holds the earliest patents for HIP casting, with applications to aluminum castings. (See the chronology at the end of the appendix.) This work preceded the efforts of Air Force contractors and subcontractors and established the concept of HI P casting explored by Battelle, General Electric, and Howmet. 2. The concept of HIP casting is the dominant attribute of the technology to be transferred. Conferences and technical reports resulting from private research and the AFML have been important contributions to the diffusion of the concept. 3. Current HIP casting equipment (which embodies the concept) is similar to the autoclave technology used for powder metallurgy and carbide production at the time of early HIP casting development. Modif ications of such equipment are necessary for HIP casting. Powder metallurgy uses lower temperatures and protects the materials in an envelope; the proximity of HIP casting temperatures to melting and the exposure of parts require closer temperature and environmental controls. Necessary operating changes are minor. 4. HIP casting researab was first undertaken to lower rework and scrap rates for cast parts. In many cases HIP casting has also improved material properties and increased the uniformity of batches of cast parts. These added benefits have been an incentive to specify HIP-cast components during the design of new products. 5. In some cases, improved investment casting techniques, directional solidif ication, single crystal castings, or use of forgings are technical alternatives to HIP casting. In other cases, however, practical technical alternatives do not exist. 19
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6. Technical questions about the design and process control for large pressure vessels have so far limited the size of BIP autoclaves and so limit the size of HIP-cast parts. One of the largest HIP facilities, installed by Pratt and Whitney in 1975, is an 80-incb high cylindrical chamber with an inside diameter of 46 inches. These size restrictions tend to make HIP casting of large components f~nancially--if not teabnically--infeasible at the present state of the art. Market Structure Conditions 1. In the aircraft engine supply market (where the HIP casting applications under study have been developed), the important participants are engine buyers, their contractors, and the contractors' parts suppliers. Primary engine buyers include defense and commercial users of jet and gas turbine engines. General Electric and Pratt and Whitney have been the important engine suppliers for this study. Parts suppliers are foundries, notably Howmet Turbine Components Corporation, Precision Castparts Corporation (PCC), and TRW. 2. Adoption of HIP casting technology teas a double meaning. A parts supplier becomes an adopter by purchasing HIP casting equipment. A contractor adopts the technology by specifying HIP-cast components in its designs. When a contractor becomes an adopter, the parts supplier may invest in HIP casting facilities, find an outside HIP casting service (see conditions ~ 3 and $4 below), or forgo bidding on the spec i f fed part . 3. Development of other HIP technologies created sources of HIP casting capacity for contractors and parts suppliers. Because of their earlier research in powder metallurgy and cemented carbide, Battelle and Industrial Materials Technology (IMT) were the major sources of HIP capacity during the development of HIP casting. More recently Battelle has avoided that role, but IMT and other firms provide HIP casting job shop services to parts suppliers. When Howmet acquired production facilities, it began to provide job shop service to other parts suppliers; TRW, for example, sends part of its HIP casting business to Howmet. Thus, parts suppliers can choose between in-house and outside HIP casting operations. 4. The availability of outside HIP casting services enables parts suppliers and contractors to experiment with the technology and adopt it gradually. As their technical experience and customer demand increase, firms may then choose to invest in their own HIP casting capacity. ~ 5. Much of the present demand for HIP-cast aircraft engine parts is for after-market components. Lead times for introducing new processes to aircraft engine production can be quite long. Adoption of new technology for full-scale production awaits a new generation of 20
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engines because of testing requirements and because of the structure of contracts between engine builders and engine users. Pratt and Whitney has specified titanium castings using HIP for both original equipment and after-market components in the F-llO program. The Air Force Materials Laboratory (AFML) became involved in HIP casting when General Electric Evendale offered the AFML laboratory evidence of feasibility in 1971. The AFML saw HIP casting as a generic manufacturing technology, beneficial to all users of castings but not likely to be developed quickly by industry. Proponents of HIP casting in the AFMD, convinced that the potential benefits were great, advocated and won funding for General Electric's work in 1972 through the Manufacturing Technology program. The AFML hoped to demonstrate the efficacy of HIP casting and to provide sufficient process specifications to allow adoption by parts suppliers. While General Electric pursued its research in Evendale, Helmet began to develop its own HIP casting process without AFML funding. Both companies can be considered originators of the technology. General Electric The Technical Systems and Materials Division of General Electric (GE) produces jet engines for aircraft, industrial, and marine applications as well as electronics and materials for space, defense, medical, communications, and computing applications. General Electric has a matrix organization, with Engineering, Manufacturing, Project Management, and Quality Control divisions in each of its plants. Two of the aircraft engine plants were included in this case study: a facility in Evendale, Ohio, primarily producing large commercial engines, and a facility in Lynn, Massachusetts, producing small military engines as well as combustors, nozzles, and frames for use in other plants. Researchers at GE Schenectady Materials and Processes Laboratory in the Gas Turbine Products Division carried out early HIP casting research and presented a paper to the Seven Springs Conference of the American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME) in 1972. HIP casting development under the AFML contract was the responsibility of a group working in the Engineering Division of GE's Evendale Plant. General Electric does much of i ts Techn ica1 Systems and Mater ials business as a direct government contractor. The firm has years of exper fence in R&D and production pro jects for the government and continues to seek government contracts. Evendale, located close to the AEML in Dayton, Ohio, follows a policy of using Air Force f unds for risky R&D that it might not otherwise undertake. Within GE, design and manufactur ing considerations are tightly coupled, but managers in the Manufacturing Technology Operation believe that product design considerations ultimately drive decisions related to production processes . 21
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Changes from wrought to cast turbine blades and the increasing blade tip speeds of the supersonic transport program fostered General Electric's initial interest in HIP casting. During 1969 and 1970 General Electric obtained laboratory confirmation of the technical feasibility of such techniques. In 1972 they acquired Air Force funds for development of a prototype. Evendale looped to use HIP-cast parts by persuading the foundries that supply cast engine components to adopt HIP casting techniques. In 1974 General Electric completed its first AFML contract in HIP casting, an investigation of its application to aluminum and superalloys. That year the firm received another AFML contract, to obtain data for titanium and three other superalloys. Howmet Turbine Components Corporation Howmet believes itself to be the largest supplier of turbine blades to the U.S. aircraft industry. A wholly owned subsidiary of Pechiney Ugine Kuhlmann of France, Howmet specializes in the production of investment castings used in the hot section of gas turbine engines. In addition, Howmet produces its own air and vacuum melted alloys, manufactures ceramic products for its casting operations, precision machines and coats its finished castings, and produces titanium ingot for the aerospace industry. Howmet facilities in Whitehall, Michigan, include a research center and HIP casting facilities. A materials research and development (R&D) group at the Technical Center was responsible for preproduction HIP casting research. Howmet is well established as a supplier to government contractors but prefers not to involve itself extensively in government R&D projects. Managers at Howmet believe that requirements to justify and generalize federally funded researob force contractors to undertake additional work that does not benefit them. They prefer to retain maximum control over the nature and duration of R&D projects. Howmet has an aggressive R&D program for its own purposes and considers itself to be the leading supplier of high-technology cast higb-temperature engine components. In 1965 owlet researchers began to investigate applications of HIP for closure of porosity in titanium- and cobalt-based alloy castings. The research was completed in 1967, with positive results for titanium. A Howmet team investigating techniques for elimination of microshrinkage attended a conference of the AIME in 1972. There they heard a presentation on HIP casting given by workers from GE Schenectady. After the conference Howmet researchers recovered the results of earlier Howmet research and initiated development using powder metallurgy facilities at Industrial Materials Teabnology (IMT) and, later, at Battelle. 22
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By 1974, with about 3750, 000 invested in R&D, Bowment was HIP casting several of its customers' parts and considering purchase of its own HIP casting facilities. Howmet continued to monitor General Electric's work while developing HIP casting technology to production readiness . Howmet developed casting preparation procedures, post-EIIP heat treating routines for restoration of material properties, and established process tolerance for a wide variety of its customers' alloys. Adoption of HIP casting in the aircraft engine industry occurs in two ways. First, contractors attracted by the potential cost ravings and materials properties resulting from the technique may place orders for HIP cast parts with their subcontractors. These orders may be for experimental work, development, after-market components, repairs, or production. Second, parts suppliers may decide that demand justifies the purchase of HIP casting equipment. Parts suppliers that have not adopted the technology may employ the services of outside HIP casting f acilities such as those of IMT and Battelle. The decision to adopt frequently follows a period of using outside HIP casting services. Parts Suppliers Howmet Turbine Components Corporation Howmet, at the completion of its HIP casting development project, had to decide whether to continue to subcontract for HIP casting or to acquire its own equipment. Investment costs were f irst estimated in 1974 as $1 million. In 1975 Howmet tried to organize a joint venture with two of its major customers to share the ri sks and profits of TIP casting equipment. Howmet presented evidence on the improved and more uniform properties of HIP~ast components. The firm's customers, whose analyses focused on projected rework and scrap cost savings, declined to join Howmet in investing in HIP casting. After hesitation, Mowmet decided to assume the risks of investment alone. Approval was given for purchase of a pressure vessel from Automation, Inc., and a furnace designed and produced by Battelle. In making this decision, Howmet let commitment to technological leadership be the deciding factor. Full production began in 1977, with the largest order placed by GE Evendale. In 1978 Howmet built another furnace under license from Battelle at a cost of $80, 000. At present Howmet's titanium casting division augments demand for HIP casting of engine components. Howmet also offers HIP casting services to other parts suppliers. 2. TRY TRW is a major competitor to Howmet in the turbine blade market but not in titanium. Researabers at TRW first considered purchasing HIP 23
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casting facilities in 1972, when General Electric' s work in the area became widely available. Like other parts suppliers, T]W's options included improvements in casting processes and contracts for outside H IF services . Volume was the primary consideration for TOW. They found that requests for airfoil HIP castings were too limited to support the expense of in-house equipment. TRW lacks the titanium work available to the Howmet HIP casting operation and was not interested in providing a HIP casting service to other parts suppliers. On this basis, TOW has elected not to purchase HIP casting equipment. Bowmet and IMT do much of the HIP casting work for TRW. Recently, TRW has approved the purchase of a small HIP casting unit for research and development. The company reviews annually its decision not to purchase HIP casting equipment for production. Precision Castparts Corporation Precision Castparts Corporation ~ PCC) is a supplier of large aluminum and superalloy investment castings (e.g. structural components for large gas turbine engines) and engine airfoils. It began supplying HIP-cast components before 1976 but does not have its own HIP casting capacity. PCC sends its large components from its Portland, Oregon, location to Crucible, a Pittsburgh-based foundry. Industrial Materials Technology HIP casts PCC' s sma' 1 components in a Portland facility that depends on PCC' s business . Precision Castparts Corporation's decision not to adopt HIP casting by purchasing equipment is based on its customers' demand. GE Evendale is at present PCC's largest user of HIP-cast parts. Pratt and Whitney is in the process of evaluating several substantial commitments to HIP castings from PCC. Fiat, MTU (Germany), and a mix of smaller customers provide the balance of the demand. PCC and IMT are both prepared for the eventual acquisition by PCC of IMT's Portland facility. PCC is also considering the purchase of equipment suitable for large structural HIP castings if sufficient demand develops. Engine Builders: GE Lynn Engine builders provide the demand for HIP castings which drives the investment decision of the part suppliers. Within GE, the demand entails technology transfer from engineering materials researab to engineers responsible for the design and production of specific engine programs. Material processing innovations at GE are often developed during an ongoing engine production program but not fully adopted until a later engine goes into development. The transfer of HIP casting to GE's Lynn 24
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Aircraft Engine operations, still in process, seems to fit this pattern . At present, GE Lynn is in the early stages of adopting the techniques first developed by the Engineering Division materials R&D group in E`rendale in 1972-74. Three obstacles have slowed adoption of HIP casting at Lynn. 1. Equipment Availability -- until recently HIP casting was available only from Battelle (which wished to avoid production cost itments) and IMT. Growth of IMT' ~ capacity and Howmet' s new operations suggest that when GE Lynn is ready to adopt fully HIP castings, production capacity will be available. 2. Engineering Confidence -- Materials engineers require full documentation of materials properties at the operating conditions of the engine in question. Though Evendale teas supplied verification of materials properties at some temperatures, these temperatures are not necessarily the same as those for which current engine components are designed. Development of materials data, especially low and high cycle fatigue and stress rupture properties, will be carried out in Lynn. Adoption requires operating experience with HIP-cast parts. At present, HIP casting is becoming an unapproved repair procedure. Once this is accomplished, HIP-cast parts will be verified with at least 150 hours of factory engine use. 3. Contract Cost Controls -- HIP casting can add $200-$300 per engine in foundry costs that are subject to the scrutiny of project cost accountants. Offsetting savings in rework and ship time are included in overhead and are not as readily visible to cost controllers. Further, GE's customers already have a workable contract and are only gradually being educated to the benef its that justify what appears to be an expensive change in production techniques. Introduction of HIP casting through the design and development of new engines avoids these obstacles. During development designers can take full advantage of improvements in materials properties afforded by HIP casting and gain engine use verification of materials properties during engine testing. GE is very likely to specify HIP~ast components for future engines, though GE engineers expect to continue their efforts to improve conventional casting techniques as well. 25
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HIP Casting Chronology 1967 : Alcoa, working with Battelle, patents the concept of HIP casting for aluminum. 1965-67 : Howmet performs research on HIP castings of titanium- and cobalt-based alloys. 1971-72 : GE offers evidence of feasibility to the AFML. Mowmet, after hearing a report from GE, recovers past research and begins R&D. 1974 : GE completes its first AFML contract, reporting success in densification of Rene'80 and Ti-6 Al -4V castings. 1975 : Hbwmet commits to capital investment in HIP casting facilities. 1976 : Testing, development, experimental, and after-market use of HIP-cast components. 1977 : H~wmet begins full production. 1978 : Howmet invests in additional production capacity. 1980 : GE completes its second AE?ML study, Manufacturing Methods for Low Cost Turbine Engine Components of Cast Superalloys. n 26
Representative terms from entire chapter: