The Laser Cladding In Situ Generated Particles Reinforced Ni Matrix Composite Coatings

Synthesis of metal matrix composites (MMCs) by surface incorporation of reinforcement particles on various substrates for providing a better performance has attracted extensive attention in recent years. Among the various synthesizing techniques, laser surface alloying or laser cladding is a promising technique because it can produce the desired shape and distribution of the reinforcement phase, thus providing remarkable enhancement on corrosion resistance, wear resistance and thermal conductivity without impairing the bulk properties.However, the majority of reinforced phases are directly added into coating materials.When the surface of the particles is not clean or is polluted, crack may propagate from the interface. The in situ composite method, has been extensively studied to produce composite materials, by which the interface problem could be voided. In this method, reinforcements are formed in the matrix by reacting between added pure elements or compounds. The reinforcements may be more compatible with the matrix and the interface may be cleaner than that of composites made conventionally. Because the in situ formed dispersions are thermally stable, this will ensure that the composite matrix has sufficient strength to transfer stress.The main results and conclusions as shown as the following: 1, Good finish and in situ synthesized B₄C particulate reinforced composite coatingscan be successfully achieved employing a proper amount of (B₂O₃+C)-dopingunder a suitable laser power and scanning velocity. 2,B₄C particulate are formed in the matrix by reacting between added pure boronoxide and graphite. The reinforcements may be more compatible with the matrixand the interface may be cleaner than that of composites made conventionally.The in situ formed dispersions are thermally stable, and this will ensure that thecomposite matrix has sufficient strength to transfer stress. 3, Because of the generation of B₄C particulate and the uniform dispersedness ofthese particulates in the matrix, the composite coatings give very high hardness of...