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. After the test specimens were prepared from the steel, the surface heat treatments; carburizing, carbonitriding and a practical type of treatment involving the first nitriding then carburizing was done on samples. Fatigue tests of the rotational bending type performed on samples. In addition, microhardness and microstructural evaluations were used to analysis the achieved results from the fatigue tests. 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 applying surface heat treatments. Also, the initiation region of the fatigue crack from the sample's surface has been transmitted to the interface of the hardened layer and the base metal in surface-treated steels. Also reduction in the number of crack initiation places in the treated samples is specified compared to raw samples.