Microstructure and mechanical properties of tungsten carbide-reinforced commercially pure Ti matrix composite coatings deposited by laser cladding

Commercially pure titanium (CP Ti) exhibits excellent corrosion resistance and formability. However, its relatively low hardness limits its use in applications requiring wear resistance. In this study, tungsten carbide (WC)-reinforced CP Ti composite coatings were deposited on CP Ti (Grade 2) substrates via laser cladding using a laser-directed energy deposition system without preheating. A representative process condition of 2,300 W and 500 mm/min was selected based on the dilution ratio to avoid excessive dilution while ensuring metallurgical bonding, and no visible cracks were observed after penetrant testing and polished surface examination. Microstructural and phase analyses showed that WC addition increased the retained β-Ti fraction through W dissolution and β stabilization, while promoting the in situ formation of TiC carbide phases around partially unmelted WC particles. Consequently, the microhardness increased from 242 HV at 0 wt.% WC to 511 HV at 30 wt.% WC. Ball-on-disk tests revealed that increasing the WC content significantly reduced the wear depth and improved wear resistance, although the coefficient of friction exhibited greater fluctuations. Additional SEM/EDS analysis of the worn WC counterface balls showed that W-rich debris could originate from the coating, the counterface ball, or both, indicating debris-assisted three-body abrasion at higher WC contents. Potentiodynamic polarization tests in 3.5 wt.% NaCl solution further showed improved corrosion resistance for the WC-containing coatings. These results demonstrate that WC addition effectively controls β-Ti stabilization, carbide formation, hardness, wear behavior, and corrosion resistance in laser-cladded CP Ti-WC composite coatings.