The Study Of In Situ Synthesized Particulate Reinforced Ni-Based Composite Coating By Laser Cladding

In situ synthesis of ceramics particulate reinforced metal composites by laser cladding on various substrates is an advanced surface modified technique. It provides coatings have a better performance, combined high intensity and high toughness of metals with the properties of ceramics, such as high wear resistance, high corrosion resistance and antioxidant.There are two primary ways to bring reinforced phases, including additional doped and in-situ synthesis of ceramic particulate. Compared with the coating of additional doped, in situ synthesized ceramic phases are thermally stable, which nucleated and grew up in the matrix, and the coating has a cleaner surface and homogeneous dispersion, with better compatibility with metal matrix and higher bond strength.In order to obtain composite coating with good wear resistance, laser cladding of Ni60+(Ta2O5+Nb2O5+C) and Ni60+(Nb2O5+V2O5+C) on A3 steel were performed. The microstructure and phase analyses were performed by scanning electron microscope, energy-dispersive spectrometer and X-Ray diffraction. The microhardness and wear resistance were investigated by a microhardness tester, wear and tear testing machinery.The results of Ni60+(Ta2O5+Nb2O5+C) composite coating showed that good morphology and improving performance of TaC-NbC particulate reinforced comp-osite coating has been successfully synthesized by laser cladding on A3 steel with the proper proportion and the suitable conditions. The microstructure of the coating was mainly composed of a large number of the white stellate TaC-NbC particulate phase and the black Cr3C2 acicular phase, both of which were dispersed in the y(NiFe) solid solution phase. The hardness of the TaC-NbC particulate-reinforced composite coating was enhanced to HVo.31200. Wear tests showed that the wear weight loss of TaC-NbC coating was reduced by one third than a pure Ni60 coating, which is attributed to the presence of in-situ synthesized TaC-NbC ceramic particles and their homogeneous distribution in the cladding layer. The results of Ni60+(Nb2O5+V2O5+C) composite coating showed that good morphology and high performance of NbC-VC particulate reinforced composite coating has been successfully synthesized by laser cladding on A3 Steel. The optimum parameters are 20wt.%(Nb2Os+V2Os+C) in the mixture powder,1.8 kW laser power and 2 mm/s scanning speed. The upper and center cladding consists of a great deal of the NbC-VC particulate phase and the Cr3C2 acicular phase, which were both dispersed in the y(NiFe) solid solution phase. The hardness of the NbC-VC particulate-reinforced composite coating was enhanced to HVo.31150. Wear tests showed that the wear weight loss of NbC-VC coating was reduced by one third than a pure Ni60 coating. The improvement of wear resistance owes to the presence of in-situ synthesized NbC-VC ceramic particles and their uniform distribution in the cladding layer.