Laser Additive Manufacturing of Metal Matrix Composites

Current trends in the mechanics and energy industries impose increasing demands on metallic
materials, combining elevated service temperatures and severe mechanical solicitations. Metal
matrix composite coatings with ceramic reinforcements are good candidates in view of
fulfilling the requirements for an improved mechanical durability, and for other complex functions (e.g. self-lubrication, biocompatibility...). First of all, this paper provides an introduction to metal matrix composites with a particular attention for the process known as laser cladding that appears as a promising technology for making composite coatings. In this process, a (mixture of) metallic powder(s) is projected onto a substrate through a nozzle and simultaneously melted by a laser beam. Laser cladding is characterised by ultra-fast solidification and cooling rates, thus giving rise to ultra-fine microstructures and potentially enhanced mechanical properties. The paper thus focuses on the relationships between the thermal history during the production of a composite coating, and the resulting microstructure and properties, with special attention to the dissolution of ceramic particles (e.g. carbides) and to interfacial reactions taking place between the particles and the metallic matrix.