Promoted low-temperature plasma nitriding for improving wear performance of arc-deposited ceramic coatings on Ti6Al4V alloy via shot peening pretreatment

Abstract

In the present work, the combination of shot peening (SP), low-temperature plasma nitriding (PN) and arc deposition (AD) is proposed to improve the wear performance of Ti6Al4V alloy. The low-temperature rapid nitriding of Ti6Al4V alloy was realized by SP pretreatment to obtain a desired nitrided interlayer. The high-density structural defects produced by SP pretreatment promote the nitriding kinetics at low temperature. The nitrided interlayer consists of an outermost TiN/Ti2N compound layer and an inner diffusion layer, showing a diffusion-typed hardness-profile, which is beneficial for the enhancing of adhesion strength and load-bearing capacity. Moreover, the improvement of adhesion strength is associated closely with TiN/Ti2N compounds which can provide heterogeneous nucleation sites for AD coating with a high hardness of about 3100 HV. The high bearing-load capacity and adhesion strength can ensure the excellent wear resistance of SP-PN-AD-coated sample when compared to single AD or PN-AD samples, especially under intensive wear load conditions. The present work provides a new insight into surface hardening of Ti alloys.

Keywords

• Low-temperature nitriding
• Shot peening
• PVD
• Ceramic coating
• Tribological properties
• Titanium alloy