Corrosion behavior and wear resistance of Zr-2.5Nb alloy after thermal oxy-nitriding treatment

Nitrogen oxides of metals are hard and have excellent electrical conductivity, and have a wide range of applications in structural materials and industrial production. The aim of this study is to modify the surface thermal treatment of alloys and optimise the process parameters so that the corrosion and wear resistance of alloys can be significantly improved, extending service life. The Zr-2.5Nb alloys were experimentally selected for thermal treatment from 700 to 1200 °C in a vacuum tube furnace under N2 and O2. The morphology and surface element distribution were investigated. ZrN, ZrO2, NbN, and Nb2O5 composite film were generated on the alloy surface, which was relatively thick and dense. The impedance and polarization curves of specimens were investigated in NaCl and HCl solutions. All of the treated specimens exhibited good corrosion resistance and pitting resistance compared with that of the substrate. Results of Vickers hardness and friction wear test performance revealed significant quality improvement. Both wear volume and wear mass decrease gradually. The thermodynamics of the thermal treatment process was analyzed via the calculation of the Gibbs free energy.