Intermittent vacuum gas nitriding of TB8 titanium alloy

Abstract

TB8 titanium alloy is a new type of metastable β titanium alloy, an intermittent vacuum gas nitriding (IVGN) process was used to improve its surface hardness and wear resistance. The phase constitution and microstructure of the surface-modified layer were measured by XRD and SEM, and the surface hardness and wear resistance of the treated samples were also analysed. The results showed that the surface activity of the samples was greatly improved and the diffusion of nitrogen into the substrate was promoted by the IVPN process. After the IVPN treatment at 780 °C for 4 h, a dense nitrides layer and a nitrogen diffusion zone of considerable depth were formed on the surface of the TB8 titanium alloy. TiN, TiN0.3 and Ti2AlN were the major phases on the nitrided surface. The surface hardness of the IVPN sample reached 850–900 HV, which is three times as that of the substrate. Due to the formation of a gradient hardened layer and the high bonding strength of the nitriding layer with the substrate, the wear resistance was greatly improved.