Plasma surface alloyed Ta diffusion layer and Ta coating on Ti6Al4V alloy: Mechanical and wear properties

Abstract

In this study, a pure Ta diffusion layer and Ta deposition coating were diffused and deposited on the Ti6Al4V substrate by the double glow plasma surface alloying technique. The surface morphology, cross-sectional element distribution, and phases were characterized by SEM, energy-dispersive x-ray spectrometer (EDS), and XRD. Both the mechanical properties and the wear resistance were investigated through the nanoindentation test and reciprocating friction-wear test. In addition, wear simulation was also examined. Ta deposition coating showed a denser and typical cauliflower structure. The Ta diffusion layer, however, exhibited two distinct types of structure: cellular grains and a kind of structure, aggregated and white, with a greater concentration of the Ta element. The cross-sectional morphology and the EDS result showed that a metallurgical bonding was developed between the coating and substrate. In addition, based on the result of nanoindentation, the Ta diffusion layer had higher hardness, elastic modulus, and initial yield strength than that of Ta deposition coating. However, the reciprocating friction-wear result revealed that the Ta deposition coating displayed better wear resistance compared with the Ta diffusion layer due to the thin thickness and inhomogeneous Ta element concentration. The wear simulation result revealed that the stable highest contact temperature is 103.7 °C by nonlinear curve fitting, and the Ta diffusion layer showed the highest equivalent stress.