Co-based and Co/WC Laser Metal Deposition: A Comparative Study between Continuous and Pulsed Wave Laser Process Conditions

Laser metal deposition (LMD) has attracted global interest due to its capacity to fabricate wear-resistant materials. However, the magnitude of heat input is crucial during the manufacturing of hard-facing alloys. This study explores the potential of LMD to deposit Co/WC composite coatings using different laser beam emission modes—specifically, continuous and pulsed waves. Co-based coatings without WC were also fabricated for comparative analysis. The primary characteristics of the coatings, including macro- and microstructural evaluations, chemical and phase composition, hardness, and wear resistance, were systematically studied and compared to laser emission type, track overlapping percentage, and laser delay time. Results indicate the homogeneous distribution of hard WC particles along the coatings, regardless of the process parameters. A notable finding is the fine-grained microstructure developed when employing a pulsed-wave laser condition, further enhanced with increased delay time. The pulsed-wave mode inhibits the dissolution of WC particles, whereas secondary carbides are formed in the coatings under continuous-wave mode. The hardness of Co/WC composite coatings is 1.2 to 1.5 times higher than that of Co coatings. Partial WC dissolution positively influences the wear rate of composite coatings, reducing its value by 1.9 to 3.7 times.