Enhancement of wear and corrosion resistance of metal-matrix composites by laser coatings

A novel technique based on laser-induced chemical reduction of metal salts has been developed to produce surface coatings on metal-matrix composites (MMCs). The substrate is predeposited with a paste, containing concentrated salts of the elements to be coated along with a thickening agent, and then subjected to high power laser radiation. The rise in surface temperature during laser irradiation led to the decomposition of salts to their native metals. The combination of metal and metalloid elements in the reaction zone forms an amorphous layer due to the specific chemical ratio and rapid cooling rate. The thickness of the coatings obtained were of the order of 50–100 m. The coatings exhibited amorphous and microcrystalline structures, possessed hardness in the range of 300–1700 H_v (substrate hardness 80–90 H_v), had superior sliding wear resistance and excellent corrosion resistance. The advantages of this process include the formation of complex coatings on MMCs by a simple, versatile technique which does not require any vacuum or inert atmosphere.