Influence of Cooling Rate on the Microstructure and Mechanical Properties of Different Low Alloy PM Materials
Sinter hardening is an established cost-effective process for producing high strength parts that combines sintering and accelerated cooling in one sintering cycle, and also removes the need for additional heat treatment. It is known that the cooling rate after sintering greatly influences the microstructure of PM steel through the formation of martensite, which strongly determines its final properties. Alloying elements such as molybdenum, chromium, nickel and copper all promote hardenability. By increasing the hardenability of the material, martensite can also be obtained at lower cooling rates.
In this study, a number of materials used for sinter hardening (Mo/Cu hybrid low alloy steel and Cr/(Mo) pre-alloyed low alloy steels) have been investigated utilizing various sintering temperatures and cooling rates in a new pusher/roller furnace. The mechanical properties and microstructures achieved for each individual PM material are described. By understanding how sintering temperatures and cooling rates influence microstructure and mechanical properties, it is possible to optimize the sintering cycle for each material and its applications.