Thermal Nitridation Deoxygenation and Biotribological Properties of Zr2.5Nb

Zirconium and its alloys are considered to be materials for artificial joints because of their excellent biocompatibility. In this study, we proposed the introduction of high-purity iron beads as external deoxidisers to inhibit the oxidation of Zr2.5Nb during thermal nitriding and investigated the biotribological properties of this alloy after deoxidation. Zr2.5Nb samples were subjected to deoxidation thermal nitriding at 900°C and 1000°C for 4 h. The main phase on the surface was ZrN, which was accompanied by a minor phase of unsaturated zirconium oxides (ZrO_0.33, ZrO_0.27). The thickness of the ZrN ceramic layer increased from 5.26 ± 0.37 μm to 7.78 ± 0.19 μm. During electrochemical friction–corrosion test, the open-circuit potential (OCP) and coefficient of friction (COF) values for the sample prepared at 900°C were −809.8 mV and 0.3015, and those for the sample prepared at 1000°C were −682.3 mV and 0.3168. The samples that underwent deoxidation thermal nitriding exhibited better friction–corrosion resistance and a lower friction coefficient than the original sample. Additionally, the volume wear loss was reduced by 50.53% and 62.27%, also demonstrating the superior biotribological properties achieved through deoxidation thermal nitriding.