Fatigue behavior of plasma surface modified Ti-6Al-4Â V alloy

Mo and Mo-N surface modified layers were prepared on Ti-6Al-4 V alloy using a double glow plasma surface alloying technique. Impact tests were performed to determine the critical impact load that characterizes the fatigue behavior of the plasma modified Ti-6Al-4 V alloy. Impact tests on nitrided Ti-6Al-4 V alloy specimens were also performed for comparison. Results show that all the three surface modifications have enhanced the surface hardness and load-bearing capacity of the modified Ti-6Al-4 V alloy. Cohesive failure mode was observed on all failed specimens. Amongst the three tested surface modifications, Mo modified Ti-6Al-4 V specimens have the best fatigue strength due to the excellent toughness of their surface modified layers. It seems that surface hardness and toughness of the modified layers should be optimized to ensure a better fatigue strength.