Ni–Mo 系低合金鋼粉を適用した焼結転造浸炭歯車の特性

Abstract

Finish gear rolling experiments, single tooth bending fatigue tests and gear running tests were carried out using P/M gears made of Ni–Mo pre-alloyed steel powder. A high precision CNC form rolling machine of two-roller dies transverse type was employed. The entire gear tooth flank was successfully densified from the tip to the root fillet by surface rolling. The durability test results show that the test case-carburized P/M gears with a density of 7.5 g/cm3 can achieve bending and surface fatigue strengths of 1.0 GPa and 2.0 GPa, respectively, which completely match with those of case-carburized SCM415 (0.15C–1.0Cr–0.2Mo–0.7Mn) wrought steel gears and those load bearing capacities tend to increase by surface rolling. The compressive residual stress near the gear flank surface is the level of 800 MPa, which is almost equivalent to that of wrought steel gear. The representative damages of P/M gears in gear running tests are pitting, which is the case with the wrought steel gear.