Investigation of rolling contact fatigue damage of a case-carburized low alloy steel

Experimental investigations were carried out on case-carburized En 36 A steel to study contact fatigue behaviour and pit formation. The effects of case depth, specimen hardness, different combinations of hardness of the specimen and mating roller and the influence of grinding operations before or after heat treatment were assessed. Optical and electron microscope studies revealed the formation of subsurface cracks which propagate because of the alternating shear stresses in the subsurface and which then turn towards the surface where the final failure occurs by ductile and then brittle fracture. Surface cracks initiated by micropits were also observed in some specimens. © 1977.