Microstructure and Mechanical Properties of Multiple In-Situ-Phases-Reinforced Nickel Composite Coatings Deposited by Wide-Band Laser

Metal matrix ceramic composites (MMCs) are widely applied materials in surface engineering due to their high hardness and excellent wear resistance. Recently, various MMCs have been successfully fabricated by a promising method named direct laser deposition. In this work, nickel-based hard surface coatings reinforced with multiple in-situ phases were deposited by wide-band laser. The strengthened phases were synthesized by varied content of Ti and B4C precursor powders. The microstructure evolution, phase constitution and mechanical properties of the designed coatings were investigated. Results indicated the B4C were decomposed and free C and B atoms were released in a molten pool. Multiple secondary phases such as TiC, Cr7C3, Cr23C6, TiB and CrB were in-situ synthesized. As the content of precursor Ti and B4C powders increased, the microstructure of the laser-clad coatings was greatly refined due to the plentiful in-situ phases. Mechanical properties of the coatings revealed the maximum elastic modulus and microhardness reached 247 and 7.18 GPa in the experiment group. Friction tests indicated the average friction coefficient of optimized coating was about 0.50.