Effect of WC on microstructure, molten pool and properties of Ni based coatings by multi-layer laser cladding

Ni45 powder and tungsten carbide (WC) particles were added to laser cladding coatings by to improve the wear resistance and impact resistance of mechanical components. The microstructure and elements of the coatings were assessed using SEM and TEM. A high-speed camera was used to analyse the morphology of the molten pool during the cladding process. The wear resistance and impact resistance of the coatings were tested by a wear and impact testing machine. The reaction of WC in the molten pool releases a large amount of thermal energy, which gives the molten pool a faster flow rate. The flow rate increases rapidly at WC dosages of <= 10 wt% and more slowly at dosages >10 wt%. Flow in the molten pool causes the WC to break the columnar crystals in the pool, which form a large number of coarse cellular crystals. WC causes the coatings to precipitate more rich Cr hard phase and intermetallic compounds, which increases their abrasion resistance and impact performance. The wear rate of the coating containing 12 wt% WC was 91.59% lower than that of the Ni45 coating. However, the impact resistance was decreased by the stress concentration and brittleness of the WC.