Effect of Surface Nano-crystalline Layer Formed by Heavy Plastic Deformation Process on Rolling Contact Fatigue

Abstract

This study developed a deformation process to form a uniform nano-crystalline layer with relatively high thermal stability that can retain even after an induction heating and quenching process on a surface of cylinder-shaped sample. The effect of the surface nano-crystalline layer on rolling contact fatigue life of carbon steels (JIS S45C and S55C) was investigated. The sample with the surface nano-crystalline layer showed lower friction coefficient under cylindrical rolling contact condition comparing to that without the layer. The rolling contact fatigue life was extended to 4 times higher cycles by forming the nano-crystalline layer. It is presumable that the improvement of a rolling contact fatigue is owing to not only the high hardness but also the reduction of friction coefficient during the test followed by a suppression of dynamic tempering softening and variation of stress distribution.