Effect of Laser Texturing in Thermal Spraying on the Fatigue Life of the Ti-6Al-4V Alloy

Abstract

The Ti-6Al-4V alloy is widely used in aerospace applications for its excellent mechanical properties; however, it presents low wear resistance. It is often coated with a cermet using high-velocity oxygen fuel (HVOF) spraying to improve its wear performance. The Cr₃C₂-NiCr cermet becomes particularly interesting since it is non-carcinogenic, compared to traditional cermet coatings containing tungsten-cobalt compounds. While the improvement in wear resistance of Ti-6Al-4V with this coating has been demonstrated, its impact on the fatigue performance of the alloy remains to be studied. This is precisely the aim of this study, which focuses on the fatigue life of a Cr₃C₂-25NiCr-coated Ti-6Al-4V alloy. Among the various influencing factors, surface preparation represents a significant source of crack initiation, particularly in the case of sandblasted surfaces. Indeed, the inclusion of fragmented alumina particles can produce stress concentration zones. Thus, laser texturing, which is a method involving the creation of anchoring points through controlled ablation, can be considered today as a less harmful surface preparation technique. The results obtained from cyclic tensile fatigue tests with a stress ratio of 0.1 for these two surface preparation methods, both with and without the coating, are presented in this paper.