Enhancing Fatigue Performance of Thermal Spray Coated Titanium Alloy by Shot Peening Before Grit Blasting

Abstract

Thermal spraying effectively enhances the surface properties of titanium alloys, yet the required surface roughening by grit blasting (GB) often degrades fatigue performance. This study proposes shot peening (SP) prestressing prior to GB to create a crack extension inhibition zone, thereby enhancing fatigue resistance. Simulations and experiments demonstrated that SP prestressing generates high compressive stress (~900 MPa) up to a depth of ~ 200 µm, which helps to alleviate the stress concentrations caused by these sharp protrusions from GB. Consequently, crack propagation is inhibited, preserving the fatigue strength of SP-pretreated, thermally sprayed TC4 alloys, while untreated counterparts show a 20% reduction in fatigue limit. Additionally, SP prestressing followed by GB maintains a high coating bond strength (>60 MPa). These findings advance the application of thermally sprayed titanium alloys in aerospace engineering.