Microstructure, Micro-Mechanical and Tribocorrosion Behavior of Oxygen Hardened Ti–13Nb–13Zr Alloy

Abstract

In the present work, an oxygen hardening of near-β phase Ti–13Nb–13Zr alloy in plasma glow discharge at 700–1000 °C was studied. The influence of the surface treatment on the alloy microstructure, tribological and micromechanical properties, and corrosion resistance is presented. A strong influence of the treatment on the hardened zone thickness, refinement of the α’ laths and grain size of the bulk alloy were found. The outer hardened zone contained mainly an oxygen-rich Ti α’ (O) solid solution. The microhardness and elastic modulus of the hardened zone decreased with increasing hardening temperature. The hardened zone thickness, size of the α’ laths, and grain size of the bulk alloy increased with increasing treatment temperature. The wear resistance of the alloy oxygen-hardened at 1000 °C was about two hundred times, and at 700 °C, even five hundred times greater than that of the base alloy. Oxygen hardening also slightly improved the corrosion resistance. Tribocorrosion tests revealed that the alloy hardened at 700 °C was wear-resistant in a corrosive environment, and when the friction process was completed, the passive film was quickly restored. The results show that glow discharge plasma oxidation is a simple and effective method to enhance the micromechanical and tribological performance of the Ti–13Nb–13Zr alloy.

Depth profiling analysis of the nitriding layer formed by gas nitriding of Ti13Nb13Zr alloy

“…In general, titanium alloy can obtain an outmost nitride layer consisting of TiN/Ti 2 N and an N diffusion layer consisting of TiN 0.3 after gas nitriding treatment, whose phase constituents, microstructure and thickness have significant impacts on the wear and corrosion resistance as well as biocompatibility. However, the research on the gas nitriding treatments of Ti13Nb13Zr alloy remained insufficient, and the relevant reports mainly focused on the microstructural development and the characterization of the required surface properties [10], while did not clarify the nitriding mechanism and the exact relation between the elemental composition, phase constituent and property evolution in the nitriding layer. In fact, these played crucial roles in determining nitriding parameters to achieve optimum properties of nitriding layer.…”