Synthesizing, microstructure and microhardness distribution of Ti–Si–C–N/TiCN composite coating on Ti–6Al–4V by laser cladding

Abstract

A micro-textured Ti–Si–C–N/TiCN composite coating was obtained using laser direct cladding method. A mixture of 20wt.% SiO2 and 80wt.% TiC0.3N0.7 was used as the precursor. A metallurgical bonding at the interface was achieved. Variation in the laser scan speed appeared to have no detectable influence on the evolution of phase type in the modified surface region. All samples demonstrated the presence of the same phases such as Ti3SiC2, TiC0.3N0.7, and Ti2O. The average crystallite size and the average surface roughness Ra of the coatings presented a decreasing trend with increasing laser scan speed. Laser scan speed has an obvious influence on the thickness and the microstructure of the coating. The microhardness in the coating depends on laser scan speed. It increased first, followed by a decreasing trend with increasing laser scan speed, and got a maximum value of about 1400HV at laser scan speed of 3mm/s, which is more than 4 times of that of titanium substrate. Ti–Si–C–N coating distributes in a distance of about 100μm.