2019 Volume 24 Pages 13-20
In order to improve the thermal fatigue strength of EDMed molding dies, thermal fatigue tests of the treated surfaces by large-area electron beam (EB) under various conditions and gas nitriding were conducted. The thermal fatigue characteristics of the treated surface were evaluated by surface roughness measurement, microscopic observation, and X-ray residual stress measurement. These results indicate that the EB treatment has more dominant influence on the residual stress than pre-processing, such as EDM and milling, and the residual stress of EB treated surface is released in the early stage of the thermal fatigue test. Moreover, the gas nitriding treatment can inhibit the heat crack generation and its propagation on the surface in the thermal fatigue test.