31.5.2000 Pressing & Sintering

Evaluation of Sinter Hardening of Different PM Materials

PM² TEC 2000, in New York, USA. Author: Ulf Engström. The development of new materials and cost effective processes are two main factors that have contributed to the growth of PM parts during the last decade. Sinter-hardening , which utilises high performance materials in combination with an accelerated post sintering cooling rate, is one exampleof such material and process development. As this technique is a one step process it combines good manufacturing economy with the ability to achieve a unique combination of mechanical properties. By controlling the post sintering cooling rate, the microstructure can be manipulated to form the required amount of martensite to obtain the desired mechanical properties. Alloying elements such as molybdenum, chromium, nickel and copper all promote hardenability. By increasing the hardenability of the material still large amounts of martensite can be obtained also at slower cooling rates. In this paper a number of different PM materials are evaluated after sinter-hardening. The influence of alloying system and cooling rate on both microstructure and mechanical properties will be discussed