Improvement of fatigue life of electrical discharge machined AISI D2 tool steel by TiN coating

This work presents the effects of titanium nitride (TiN) coating by physical vapor deposition (PVD) on the fatigue life of AISI D2 tool steel, which was electrical discharge machined (EDM) at various machining parameters, such as pulse current and pulse-on duration. Surface hardness, surface roughness, residual stress and fatigue strength were measured. Experimental results indicate that EDM treatment has a detrimental effect on fatigue life. The EDMed specimens further coated by TiN exhibited considerably increased hardness, a better surface finish, and decreased superficial tensile residual stress, or added compressive residual stress on the surface, increasing their fatigue limit. The TiN coating is recommended as an effective method for improving the fatigue life of tool steel that is being electrical discharge machined.