Fatigue Behavior Optimization of the 16MnCr5 Steel Used in Machine Tool Spindle via Different Surface Treatments

Since the sub-axis of machine tool spindles subjected to fatigue loading, the effects of different surface heat treatments on fatigue behavior of 16MnCr5 steel have been investigated in the current work. The steel specimens were prepared and surface heat treatments including carburizing, carbonitriding and a practical type of treatment involving an initial nitriding followed by carburizing were done on samples. Rotating bending fatigue tests performed on the samples. In addition, microhardness and microstructural evaluations were applied to analyze the achieved results. The fatigue fracture surfaces were evaluated by scanning electron microscopy (SEM). The results showed that the fatigue strength of the samples has been improved considerably by the use of surface heat treatments. In addition, the initiation region of the fatigue crack from the samples surface has been transmitted to the interface of the hardened layer and the base metal in the surface treated steels. Also a reduction in the number of crack initiation places in the treated samples is specified compared to raw samples.