Microstructure and Mechanical Properties of a Ti-6Al-4V Titanium Alloy Subjected to Laser Cladding

The low hardness and poor wear resistance of Ti-6Al-4V titanium alloy limit its application. The laser cladding technology is widely used in material surface modification engineering. In this study, TiO2 layers were deposited on Ti-6Al-4V titanium alloy surface by coaxial laser powder cladding method with varying laser power (600 W, 800 W and 1000 W) and cladding times (1 and 2) to improve its surface mechanical properties. The mechanical properties of the original Ti-6Al-4V alloy substrate and clad samples were then investigated and compared. The microstructure formation mechanism of the TiO2 cladding layer was discussed. The results showed that the sample cladded two-times with a laser power of 800W has the highest value of microhardness (1583.2 HV0.1), nanoindentation (9.42 GPa), and Young's modulus (197 GPa) and lowest specific wear rate (1.42 x 10-2 mm3/Nm), which indicates excellent wear performance and surface hardness. The enhancement in the surface properties was attributed to both the dendritic structures that developed during the laser cladding process and the equiaxed crystals that were diffused in the interstices of coarse dendrites. The surface strength is significantly aided by reduced grain size and inter-grains spacing.