Cold-Sprayed Metal Matrix Composite Coatings

Metal matrix composites (MMCs) combine high-hardness materials, such as ceramics, with ductile metal matrices. The resulting MMC material often has excellent strength and toughness due to the addition of hard reinforcing particles in the matrix. Typically, MMCs can be created by sintering, hot pressing, extrusion, pressure infiltration, reaction processing, or thermal spraying. However, most of these techniques are expensive and require high temperatures. Cold spraying is an innovative and cost-effective technique to manufacture of MMCs. Cold spraying relies on the plastic deformation of particles upon impact to fabricate coatings. Hard-facing particles used in MMCs typically do not plastically deform and can fracture upon high-velocity impact. It has been found that ceramic particle velocity, size, and morphology may have a significant influence on ceramic deposition efficiency. Cold spraying mechanically blended metal-ceramic powders can result in MMC ceramic content of approximately 30 vol.%, while cold spraying with composite powders can achieve ceramic content up to 52 vol.%. In addition, due to the high-velocity impact of the particles in cold spraying, ceramic powders in the feedstock provide additional enhancements to the properties of the deposited MMCs. It has been found that the addition of ceramic particles improves the deposition efficiency of the blended powders, increases pull-off bond strength, and increases the bonding within the coating. This chapter will highlight the research that has been conducted to improve the deposition efficiency of the ceramic particles and their impact on the cold-sprayed MMC material system.