Abstract
Vacuum-gas nitriding process is an effective method for controlling the thickness of nitride layer on the surface of hot die steel. This study has been carried out for increasing the life of die steel. Thermal fatigue characteristics of samples treated by the vacuum-gas nitriding process were evaluated by means of thermal fatigue test, erosion test and X-ray analysis. Fe2-3N nitride layer was not observed by the X-ray analysis in the surface layer of the sample. The hardness of sample surface was in the range of HV 800900, which was lower than that of the tufftriding sample, i.e., HV 12001400. Erosion resistance was lower than that of tufftriding sample. It was found that the thermal resistance increased by the vacuum-gas nitriding process and the nitrogen concentration in the diffusion layer formed by the process did not change during the thermal fatigue test.
