POWDERS AND PROCESSES FOR HIGH-PERFORMANCE PM STEELS

Development of new PM materials and processes has led to an increased use of PM machine components. Due to their good mechanical properties it is possible for them to fulfil the demand for high performance applications such as connecting rods, highly loaded gear box parts, transmission gears, etc. The competitive advantage of PM is primarily the net shape achievable with a minimum of operations. The dimensional tolerances are therefore of the greatest importance; especially for high strength materials which cannot be sized, the dimensions must be very close to those required after sintering. This has led to the development of powders such as the Distaloy grades or bonded powder mixes such as Starmix. The objective of these powder types is to reduce the range of alloying composition and thereby improve tolerances. This paper describes some high strength materials and the influence of processing parameters on their dimensional tolerances. In order to meet the demanding requirements of new applications it is shown that the advantages of diffusion alloyed powders, prealloyed powders, and bonded powder mixes must be used.