A. Klekovkin, N. Nandivada, D. Milligan, North American Hoganas, Inc., Hollsopple, PA
Powder Metallurgy (PM) is a cost effective alternative to traditional manufacturing processes combining high material utilization, complex net shape capability, tight tolerances, and low energy consumption. Heat treatment of recently developed materials in combination with advances in PM compacting and sintering technologies have resulted in materials with heat treated properties similar to SAE 4140 steels. This paper will investigate the properties achieved using chromium and molybdenum pre-alloyed PM steels and different processing routes. The properties achieved after various compaction, sintering, and heat treatment cycles will be evaluated.
Summary: Heat treated properties of several powder metallurgy Cr-Mo pre-alloyed steels, including
Astaloy CrL and Astaloy CrM (1.5%Cr/0.2%Mo and 3%Cr/0.5%Mo), will be presented. Test specimens were prepared to densities up to 7.5 g/cm3 by various compaction techniques and then sintered at temperatures up to 2336°F (1280°C). The test specimens were then heat treated using atmosphere carburization, vacuum carburization, and neutral hardening. The tensile strength, bending fatigue, microindentation hardness, dimensional stability and microstructures will be discussed. Recommendations for heat treatment parameters to achieve tensile strengths for of case hardened materials up to 160000 psi will also be presented.
