Microstructure Evaluation and High-Temperature Wear Performance of Hard Protective Layer Deposited on Titanium Alloy via Laser Metal Deposition

To improve the poor wear resistance of titanium and its alloys, a blended powder consisting of 60 wt% tungsten carbide (WC) and 40 wt% NiCrSiBC was produced by Laser Metal Deposition (LMD) on the surface of Ti–6Al–4V (α + β) titanium alloy. A 3 KW TRUDISK 3001 Yb:YAG disk laser (1030 nm wavelength) attached with a coaxial jet nozzle coupled with a powder feeding system was used in this study. Different powder feeding rates were used aiming to make the LMD process more economic. In addition, the deposited layer performance at elevated temperature was also evaluated. The results showed crack-free structures when using the optimized conditions. At a powder feeding rate of 20 ɡ min⁻¹, the matrix structure consists of a small continuous network of WC granular clusters in a solid solution of Cr in Ni and Ti alloy matrix. In contrast, at higher powder feeding rates of 40 and 60 ɡ min⁻¹, such granular clusters transformed into mostly fragile needle-type and rod-type W₂C that grew epitaxially from the surface of the partially melted WC particles, respectively. The results showed an increase by more than four folds in the microhardness values of the clad layers in addition to a significant wear resistance at 500 °C compared to that of Ti–6Al–4V substrates. A reduction by 66% in the friction coefficient at 60 ɡ min⁻¹ was recorded as compared with the as-received samples. Such improvement in surface properties at elevated temperatures meets the industrial requirements for such engineering alloys.