Effect of Microstructure on the Rolling Contact Fatigue Strength of 4600 Steel P/M Compacts

摘要

Generally, the mechanical properties of conventional P/M materials are inferior to those of wrought materials. Therefore, the improvement of mechanical properties for P/M materials is needed for heavy-duty applications such as automotive transmission gears. Heat-treated 4600 steel MIM compacts with heterogeneous microstructure, which are made possible using mixed elemental powders, showed excellent tensile and bending fatigue strength in our previous studies. This study was performed to clarify the relationship between rolling contact fatigue behavior and the microstructure in 4600 steel P/M compacts using prealloyed and mixed elemental powders. The heterogeneous microstructure using mixed elemental powders showed slightly superior properties compared with the homogeneous microstructure using prealloyed powder. Those compacts were also densified by rolling. Contrary to the prediction, the rolling contact fatigue strength of the rolled sample was on the same level as the non-rolled sample.