Abstract
ABSTRACT An investigation into fatigue strength of electrical discharge machined and TiN-coated AISI D2 tool steel is conducted. The damage model is constructed to reveal the influence of electrical discharge machining conditions on the fatigue life. The experimental results show that the fatigue life of the EDMed specimens is reduced compared to the mechanically polished samples. It is attributed to the rough surface and micro damage in the resolidified surface layer produced by EDM. The predicted results agree fairly well with the experimental results. The effects of titanium nitride (TiN) coating by physical vapor deposition (PVD) after EDM on the fatigue life is further investigated. The experimental results indicate that EDMed specimens coated by TiN exhibit considerably increased hardness, improved surface finish, and decreased superficial tensile residual stress, or added compressive residual stress on the surface, leading to extended fatigue limit. The TiN coating is recommended as an effective method for improving the fatigue life of tool steel being electrical discharge machined.