Unraveling the influence of Al particle size on microstructure and tribological properties of cold sprayed Al/B4C composite coatings

Metal matrix composites (MMCs) have been widely studied for their excellent mechanical properties. In recent years, cold spray has been successfully used as a solid-state deposition process to prepare a variety of metal matrix composites. However, in pursuit of achieving MMCs coating with excellent wear performance, retention of ceramic particles in the coating has been a great challenge. In this study, the effect of Al particle size on the retention of B4C particles as well as on the resulting microstructure and tribological properties of cold sprayed Al matrix composites was studied in detail. For this purpose, two kinds of Al/B4C coatings were prepared by cold spray (CS) using two different sizes of Al powder mixed with irregularly shaped B4C powder. Results revealed that small-sized Al particles are more conducive to the retention of B4C particles due to their faster flight speed and more quantity in the feedstock. Further, a high amount of retained B4C particles significantly improves the bonding strength, hardness, and wear resistance of the coating. With increasing B4C particles in the coating, the wear mechanism gradually changes from adhesive wear to abrasive wear.