Laser treatment and PVD TiN coating of Ti–6Al–4V alloy

Laser gas assisted processing can be used to modify the surface properties of Ti–6Al–4V alloy through the use of gaseous interaction with the laser melted surface. Laser surface melting of titanium and its alloys in nitrogen to form a layer of TiN embedded in a metallic matrix which is enriched in alloying elements has attracted considerable interest. The surface roughness of the laser-treated surface is poor, therefore, a secondary processing becomes essential. In the present study, duplex treatment of Ti–6Al–4V alloy was carried out. The alloy surface was melted initially under a controlled nitrogen atmosphere, which in turn resulted in a laser-induced nitrided surface. The resulting workpiece surface, then, was PVD TiN coated. In order to assess the wear properties of the resulting surface, friction tests were carried out. SEM, XRD and microhardness were carried out for microstructural analysis and material characterization. It was found that the adhesion of the TiN coating to the base alloy improved considerably in the case of laser-treated workpieces and smooth transition in plastic shearing resistance between the TiN coating and the base alloy enhanced the wear properties of the laser-treated surface.