1.5Cr – 0.2Mo 焼結合金鋼ローラの面圧疲労強度

Abstract

The rolling contact fatigue tests were carried out using case-carburized rollers made of 1.5Cr – 0.2Mo alloyed sintered steel and SCM415 wrought steel. Two kinds of P/M rollers having the initial density of 7.25 × 103 kg/m3 and 7.60 × 103 kg/m3 were prepared. The effects of the case-hardening depth on the rolling contact fatigue strength were mainly investigated. The failure mode of all P/M rollers was spalling caused by the cracking under the contacting surface. When the effective case-hardening depth was set to 1.2 mm or more, the contact fatigue strength after 2 × 107 cycles of surface rolled P/M rollers reached 2 GPa and the maximum surface damage depth remarkably decreased of about 0.2～0.3 mm, which is almost equivalent to the depth that maximum shear stress becomes the peak. The finite element analysis of contact stress shows that the maximum shear stress distribution descends suddenly at the position that is slightly deeper than the effective case-hardening layer, which is corresponding to the location of the maximum failure depth of spalling when the effective case-hardening depth of P/M rollers was less than 1 mm.