Effect of shot peening pretreatment on the high-temperature tribological behaviours of a TaN coating prepared via double-cathode glow plasma alloying

Abstract

Gradient coatings with excellent physical and mechanical properties show great potential for use in engineering applications. In this study, a TaN gradient-modified layer was prepared on TA15 titanium alloy by double-cathode glow plasma alloying (DGPA) with a gradient structure pretreated by rotationally accelerated shot peening (RASP). The effects of the RASP pretreatment at different speeds on the mechanical and tribological properties and microstructure of the TaN coatings were investigated. The results indicated that the crystal size was refined to the nanometre scale (41.8–71.4 nm) by RASP pretreatment, and a gradient structure layer (30–55 μm) formed, which facilitated the adsorption and inward diffusion of Ta and N atoms. The pretreated TaN-modified layer contained an interdiffusion layer with a thin deposition layer consisting of Ta 2 N and TaN. Furthermore, the pretreated TaN-modified layer maintained good wear resistance in ball-on-disc testing at 700 K, and the wear rate was only 36.9% of that without pretreatment, which can be attributed to the high hardness, elastic modulus , toughness and thermal stability of the modified layer. This work provides insights relevant to the development of a mechanical-diffusion composite process to produce titanium alloy coatings with enhanced mechanical properties and wear resistance at elevated temperature. • TaN modified layer with a gradient change of composition was prepared on titanium alloy using RASP and DGPA. • The refined surface promotes the adsorption and diffusion of Ta and N atoms to obtain a thicker gradient-modified layer. • RASP pretreatment can improve the wear resistance of TaN modified layers at high temperatures.