Sinter
hardening enables P/M parts to be hardened in conventional sintering furnaces,eliminating the need for
post sintering heat treatments A pre alloy powder(0 45Mn 0 45Cr 0 90Ni 1 0Mo),ATOMET 4701,admixed with 2 0% copper and 0 9% graphite was tested to develop high speed and high torque gears used for rechargeable power hand tools The parts were pressed to a green density of 6 85g/cm 3 and sintered in an endothermic atmosphere at 1120℃ for 30 minutes The apparent hardness of as sintered parts reached 37 HRC at 6 8g/cm 3 The microstructure analysis revealed a full martensite transformation occurred in the cooling zone of the sinter furnace The parts were subsequently tempered at 180～210℃ for 0 5 to 4 hours The
sinter hardening material yielded the optimal combination of mechanical properties and gear tooth accuracy after tempering at 180℃ for 2 hours,which were superior to the heat treated low alloyed material