| Laser technique has been developing rapidly since the first laser came out. Laser had been used in improving surface properties of metal materials, and now, laser surface treatment has been one of major high-energy beam technique to improve surface properties. Laser surface treatment includes transition hardening, laser remelting, surface alloying, cladding, impact hardening and so on. In these techniques, cladding is a technique to clad a layer whose properties are different from those of substrate and which is metallurgical bonded with the substrate. Laser cladding technique has been concerning by material scientists, and has been used in production, but much cladding use such as nickel based, cobalt based, and Fe based self-fusing alloy power, and although these cladding layers can improve hardness, heat resistance, corrosion resistance and wear resistance of materials, they do not resist strong sliding wear, pounding wear and particle wear. So material research men develop a new technique laser clad ceramic-metal composite coating (LCCC) by adding ceramic to the above three kinds of power. LCCC is one of laser surface techniques that are high practical value techniques and show high prospects in industry application.Laser clad ceramic-metal composite coating (LCCC) is a technique to clad a layer of ceramic-metal composite material with high hardness, excellent thermal stability, corrosion resistance and wear resistance on the conventional metal materials by laser beam, where the composite coating is metallurgical bonded with the substrate. Ceramic-metal coating has successfully combined the high melting point, high hardness and good chemical stability of ceramic phase with high strength and good ductility of metal materials, and forms a new kind of composite materials, and to prolong life span of works piece. But since the melt point of ceramic phase is much higher than that of the metal based, and their coefficient of heat expansion, elasticity modulus and coefficient of heat conduction are greatly different from those of metal based. Under the same condition of laser, temperature grade that lead to heat stress is great in the melt, and heat stress lead to pores and micro-cracks in the clad layer, which limits laser cladding greatly in industry application. In this paper, making use of the special properties such as refining crystalline grain and purifying microstructure in metallurgy, the effect of rare-earth elements on micro-hardness, corrosionIIIresistance, and wear resistance and the contributions to eliminate pores and cracks are studied by adding La2Oa or CeOa to TiC+Ni based cladding composite layer.In this paper, precoating technique of laser cladding is used to deposit TiC+Ni based alloy added La2Os and CeO2 on the surface of A3 steel substrate. The precoating technique of LCCC, the character of microstructure in laser layer, the effect of La and Ce on TiC particle (TiCp) and interactions between TiC particle and binder were studied.Using precoating technique, LCCC of TiC+Ni based alloy added La2Os or CeO2 has been achieved on A3 steel substrate. Experimental results show that porosity, impurities, and cracks in the laser layers added a appropriate amount of rare-earth oxide (LaaOa or CeCh) are decreased greatly, and the composite coatings are metallurgical bonded with the substrates. Microstructure of TiC/Ni based alloy LCCC is mainly composed of a great amount of Y -(Fe,Ni) > TiC and a small amount of (M)23Ce> NiaB phases. However, the microstructure of TiC/Ni based alloy LCCC La2O3-addtion is mainly composed of above phases and some new phases such as LaaBCv La2Ni7, and the microstructure of layer CeCh -addition has new phases as Ce3NieSi2^ CeNi2. These new phases can increase the rate of nucleating since they become as nucleus of crystalline grain, which refines the microstructures of composite coating. Distribution of TiCp, bonding strength between TiCp and binder for precoating technique are more perfect than those of the laser layer unadded rare-earth oxide. A stable region w...
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