AbstractThe effect of surface decarburisation upon the fatigue strength in rotating bending of a through hardened low alloy steel and a carburised carburising steel was investigated. The relationships between surface carbon content, depth of decarburisation, microhardness, residual stress, surface finish, and fatigue limit were examined. Whereas the fatigue limit was found to be independent of the depth of decarburisation over the range investigated (up to 1 mm), linear relationships were found between fatigue limit and surface carbon concentration and micro hardness. Furthermore, the presence of residual tensile stresses at the surface were found to lead to a reduction of fatigue limit. The fatigue limit of the rough machined specimens was found not to be significantly lower than that of the polished specimens.MST/1179