Effect of post-deposition solution treatment and ageing on improving interfacial adhesion strength of cold sprayed Ti6Al4V coatings

Abstract

This study aims at investigating the effect of post-deposition solution treatment and ageing (STA) on improving the interfacial adhesion strength in cold spray (CS) Ti6Al4V coatings de-posited on Ti6Al4V substrates, measured by the adhesive-free collar-pin pull-off (CPP) test. Solution treatment was performed at 940 °C for 1 h and ageing was carried out at 480 °C for 8 h. Investigations were carried out for specimens with three different pre-treatments of the substrate surface, namely grit-blasted, as-machined (faced on lathe machine), and ground. Additionally, the effect of post-deposition STA was studied in terms of phase analysis, microstructure, and porosity level. It was observed that STA led to complete interfacial mixing resulting in significantly improved adhesion strength (by more than 520%) with the maximum measured value of greater than 766 MPa for ground substrates, reaching 81% of the ultimate tensile strength of mill annealed Ti6Al4V.