Rolling Fatigue Life of PM Steel - Influence of Sintering Temperature and Powder Particle Size

摘要

In the present study, a lean PM steel was tested for rolling contact fatigue. Medium density PM steel (7.15 g/cm~3) sintered at two different temperatures and with two different initial powder size distributions was tested. Image analysis was performed on LOM images of cross sections to reveal the microstructure and morphology. Image analysis revealed that a smaller initial powder size distribution results in smaller pores and that a higher sintering temperature results in pores that are more circular. Materials sintered at high temperature with smaller initial powder size significantly outperformed the others when tested for rolling contact fatigue, indicating that smaller and more circular pores are beneficial for the survival of the material. Cracks were found to initiate at pore edges and propagates trans- as well as intergranular at about the depth below the surface corresponding to the largest von Mises stress.