Research Of Ni-base Alloy Welding Performance

SUS316LN stainless steel has excellent weldability properties, the material does notneed to be annealed, it can get the best corrosion resistance, but SUS316LN stainless steelhas poor wear resistance. In order to improve the wear resistance of SUS316LN stainlesssteel body, using nickel-based alloy powder RCF-202on SUS316LN stainless steel bodyparts by CO2laser.This thesis studied the laser power, scanning speed, powder feeding rate, defocusingdistance influenced on the cladding layer width, depth, height, dilution rate. Using theoptimum process parameters for multi pass laser cladding, laser cladding layer obtainedgood formability, low dilution rate, good metallurgical combination. By using X-raydiffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS)analyzed the laser cladding layer micro region size, organization structure, phasecomposition, under the optimum parameters of the melt coating hardness, wear resistancewere studied and analyzed, and its purpose was to examine whether the body laser claddingmeets the technical requirements.The optimum experimental parameters, the laser output power2.0kW, defocus amount+12mm, scanning speed550mm/min, powder feeding speed of25g/min, powder feed gasflow (Ar)2.5L/min, protective gas flow (Ar) was20L/min. After the cladding under aircooling conditions, CO2laser cladding generated transverse cracks, and effective measuresto prevent the cladding transverse cracks was to use warm-up method to completelyeliminate the cladding transverse cracks, the effective preheating temperature was≥420℃.Under optimal conditions cladding process parameters, from the surface to the lasercladding layer fusion line consists of four regions, namely the multiple primary crystalmorphology of hypereutectic organization, pine-like eutectic, hypoeutectic crystal structure,and the crystal plane. Focus on the analysis of the hypereutectic zone and the eutectic area ofthe primary crystal phase composition, the results has shown that the eutectic region of theprimary phase is composed of CrB and a small amount of Cr7C3, eutectic organizations inhypereutectic area composed of γ-Ni and Cr7C3phase, or γ-Ni and CrB phases. Because ofsmall but large CrB, Cr7C3hard phase in cladding layer, the hardness of the clad layers has been up to1035.6HV, and compares with the traditional plasma surfacing layer, the wearresistance of laser cladding layer has been increased by1.3times, fully meet the wearresistance of the valve at high temperature.