Comparison of Friction Behaviour of Titanium Grade 2 after Non-Contact Boriding in Oxygen-Containing Medium with Gas Nitriding

The surface characteristics and friction behaviour of titanium Grade 2 with modified nitride (TiN, Ti2N) and boride (TiB) compound layers were investigated. It was shown that during non-contact boriding in oxygen-containing medium of titanium, the diffusion processes take place mainly by the interscale mechanism; however, during nitriding, besides the traditional interscale diffusion mechanism, the grain boundary mechanism of diffusion of nitrogen atoms is also realized. The optimal set of surface roughness parameters (height and step parameters, a combination of kurtosis and asymmetry, and profile reference curve parameters) was obtained after boriding. It was determined that the intensity of the adhesive wear of the tribo-pairs with stainless steel and ultrahigh molecular weight polyethylene under dry sliding conditions was influenced not only by the hardness but also roughness of the modified surface layer. The lowest friction coefficient was fixed for the TiB compound layer in both tribo-pairs.