Application of lean alloy steel to PM gear
A lot of alloyed powders have been developed and are selected for PM parts. Recently, some lean alloyed powders can be used because of the cost effectiveness, however, the mechanical properties have not been clarified yet. In the past study, conventional diffusion bonded alloy powders and the lean alloyed powders were compared. As-sintered compact made from lean alloy powder didn’t show adequate mechanical properties. But the properties after heat treatment improved as almost equivalent as conventional diffusion bonded alloy powders. A typical lean alloy diffusion bonded 0.5%Ni and 0.5%Mo powder (AQ) revealed high performance. Prior investigations were done mainly by simple test specimen. In order to know the feasibility, in this study actual PM gears made from diffusion bonded lean alloy (AQ) were evaluated and the results are presented. Furthermore, the effect of surface rolling on tooth fatigue is also made clear.