Reasearch On Performance Of Laser Overlaying Welding Co-based Alloy

Laser overlaying welding is a surface improvement technology which use laser asheat source, it is complement and development of traditional surface improvementtechnology. And has the benefits unmatched by traditional surface improvementtechnology, laser overlaying welding has the advantages of overlaying welding layercomposition and dilution rate controlled, microstructures compact and uniform, processis easy automation, so that it attracted much attention in terms of surface hardeningtreatment last ten years, and has a bright prospects.SUS403is martensitic stainless steel of high heat resistance for corrosion anderosion resistance, stellite6powder has high corrosion resistance, erosion resistance,excellent wear-resistance, and high temperature resistance, it is usually used to resistextremely severe wear environment. In this paper, co-base alloys as overlaying weldingmaterials overlaying welding on the substrate of403stainless steel by YLS-6000laserand synchronized powder feeding device was prepared into laser overlaying weldinglayer with excellent performance. In this paper main studied laser overlaying weldingprocess parameters impact to surfacing layer morphology, microstructure and mechanicalproperties. The microstructure, micro area composition, phase constitute, wear resistanceand Vickers-hardness of overlaying welding layer were investigated with the lasermicroscope, electronic probe analysis, scanning electron microscope (SEM), x-raydiffraction (XRD) analysis, wear testing machine and micro-hardness tester.The experiment results showed that when the others laser overlaying weldingprocess parameters remain unchanged, with increasing the laser output power(1.4kW~4.0kW), the width of the laser overlaying welding layer increased, and overlayingwelding layer first increased and then decreased; with increasing the defocusing distance(0mm~21mm), the width of the laser overlaying welding layer increases. When the laseroutput power was too high or the laser scanning speed was too slow, the laser beamwould stay on the molten pool longer, the substrate surface would be overheating evenover-burning phenomenon; conversely, the laser power was too small or the laserscanning speed to fast, overlaying welding layer surface was appeared discontinuous, intermittent small spherical even inclusions or other defects. When the overlayingwelding process parameters at a reasonable range, we would observed the microstructureof overlaying welding layer dense and uniform, and overlaying welding layer wascombine good metallurgical with the substrate. The microstructure of overlaying weldinglayer belongs to hypoeutectic structure, the primary phases of which are composed ofCo-rich γ austenite. Moreover, the eutectic structure consists of Co-rich γ austenite andcomplex carbides(Cr23C6, CoCx, Co3W3C and WC). When the others laser overlayingwelding process parameters remain unchanged, with increasing of the laser outputpower(2.0kW~3.6kW) or the scanning speed(4.0mm/s~8.0mm/s), the Vickers hardnessof laser overlaying welding layer are first increased and then decreased, and only inappropriate laser overlaying welding parameters, the overlaying welding layer would behas Vickers hardness excellent. Because laser overlaying welding layer contains a lot ofcarbides phase, not only improve the surface Vickers hardness of test specimen from200Hv to750Hv, also the wear resistance of overlaying welding layer was enhancedabove3times.