Process maps of laser melt injection: coating property evolution with macro thermal damage of WC particles

Establishing the relationship between the energy input, particle thermal damage, microstructure, and properties is crucial for designing the particle reinforced metal matrix composite coating (PRMMCC) and developing the process maps of laser melt injection (LMI). The influence of varying energy density inputs and particle size on the surface morphology, cross-sectional characteristics, microstructure, particle thermal damage, and mechanical properties of WC particle reinforced 316L coatings was investigated. The macro thermal damage of particles was compared with the semi-quantitative evaluation results of micro thermal damage. The forms of thermal damage and evolutionary mechanisms of particles were elucidated, and the correlation between the macro thermal damage of particles and the evolutionary laws of the PRMMCC’s microstructure and mechanical properties was explored. The findings demonstrated that the PRMMCCs exhibited cracking and balling effects due to the high particle content and discontinuous molten pool at low macro thermal damage degree. Excessive macro thermal damage to particles ultimately led to the deterioration of mechanical properties. The appropriate range of macro thermal damage of LMI was determined. A process map based on the typical characteristics of the PRMMCCs was developed for LMI of WC reinforced 316L composite coating to guide coating design and industrial production.