Fatigue strength of ion nitrided steel specimens

In order to investigate the effect of ion nitration in glow discharge on the fatigue strength, ion nitrided specimens of 0.42%C, Cr-alloyed steel were tested in uniaxial fatigue. The influence of depth of nitration on the fatigue strength is investigated. The experimental investigations were carried out on a bending testing machine in constant amplitude cyclic loading and R=-1 stress condition. Microstructural, X-ray and fractographic analyses were made. The microstructure of nitrided layer is studied, the residual stresses were evaluated in the depth of the layer. Significant possibilities for increasing the fatigue strength, with about 80%, were observed.