Crack Initiation and Fatigue Behaviour Evaluation of Ceramic Film Deposited on Ti-6Al-4V Alloy

Abstract

Titanium alloy offers several material properties including strength-to-weight ratio and good fatigue properties. Wear resistance of Titanium alloy is comparatively lower. To improve its wear resistant properties surface treatment must be considered. Hard thin film deposited by PVD technique is well-known to improve the wear resistance. In this study, ceramic film (CrN) was applied to titanium alloy and its effect on the fatigue behavior was investigated. Substrate material for this work was Ti-6Al-4V. As the film hardness, crystal orientation and surface morphology were strongly depended on the bias voltage during the deposition, the ceramic film was deposited by arc ion plating (AIP) method at two different negative bias voltages. Tension-tension fatigue test and tensile test were carried out to investigate the fatigue properties. As the result, the fatigue strength was influenced by the deposition of the ceramic film, especially; the fatigue strength was remarkably decreased by the deposition of the ceramic film at high negative bias voltage compared to the uncoated specimen and the deposition of the ceramic at low negative bias voltage. On the basis of crack initiating behavior during fatigue test and tensile test the difference of the fatigue strength was also investigated.