Recent Developments

In the late 1970s, the experimental programs involving P/M wrought products began spilling over into the commercial industrial sector, principally in the form of P/M tool steels and P/M forgings. With the advent of P/M forgings, no longer were properties compromised by density. Fully dense components capable of combining the alloying flexibility and the net and near-net design features of powder metallurgy were very marketable. The later 1970s and early 1980s witnessed a significant metallurgical breakthrough in the recognition of P/M techniques for eliminating segregation and ensuring a fully homogeneous, fine-grained, pore-free, high-alloy structure. Categorized as P/M wrought metals, they led to the perfection of extremely high-purity metal powders and improved consolidation techniques such as hot isostatic pressing (HIP). The 1980s also saw the commercialization of ultrarapid solidification and injection molding technology. Both of these developments are also covered in separate articles in this Volume.

Commercial powder metallurgy now spans the density spectrum from highly porous metal filters through self-lubricating bearings and P/M parts with controlled density to fully dense P/M wrought metal systems. The P/M parts and products industry in North America has estimated sales of more than $3 billion. It comprises 150 companies that make conventional P/M parts and products from iron- and copper-base powders and about 50 companies that make specialty P/M products such as superalloys, tool steels, porous products, friction materials, strip for electronic applications, high-strength permanent magnets, magnetic powder cores and ferrites, tungsten carbide cutting tools and wear parts, rapid solidification rate (RSR) products, and metal injection molded parts and tool steels. Powder metallurgy is international in scope with growing industries in all of the major industrialized countries. The value of U.S. metal powder shipments (including paste and flake) was $1.854 billion in 1995. Annual worldwide metal powder production exceeds 1 million tons.

Trends and new developments include:

• Improved manufacturing processes such as HIP, P/M forging, metal injection molding (MIM), and direct powder rolling through increased scientific investigation of P/M technology by government, academic, and industrial research and development programs

• Fully dense P/M products for improved strength properties and quality in automobiles, diesel and turbine engines, aircraft parts, and industrial cutting and forming tools

• Commercialization of technologies such as MIM, rapid solidification, P/M forging, spray forming, high-temperature vacuum sintering, warm compacting, and both cold and hot isostatic pressing

• The use of P/M hot-forged connecting rods in automobiles and a P/M camshaft for four- and eight-cylinder automobile engines. The use of P/M composite camshafts in automotive engines and main bearing caps

A review of major historical developments in powder metallurgy is presented in Table 1.

0 0

Post a comment