Abstract
The purpose of this study is to improve an EDMed surface by application of gas-nitriding process. Evaluation of the effect was made by using thermal fatigue apparatus. Cracks prevented from growing by the nitride layer formed by the process. Total cracks seen on the section of the die steel were considerably fewer in number than EDMed one after a thermal fatigue test. It is suggested that the treatment to EDMed surfaces improves the life of die steels. Furthermore, a nitrided layer was decomposed by the thermal fatigue test and turned into a diffusion one that reduce the growth of the cracks.
