Research On Technologies And Performances Of Key Parts Of Steam Turbine By Laser Remanufacturing

Electric power industry is the basic industry of national economy.About 75% power all over the world comes from boiler-steamturbine-electric generator of heat-engine plant and reactor-steamturbine-electric generator of nuclear power station. Turbine blade is the keycomponent of steam turbine, whose life span directly influences theoverhaul life of turbine generating units. If the life span of steam turbines isincreased, the total generating capacity may raised by 1/2-1/3 withoutadding more equipments. In this thesis, 2Cr13 martensite stainless steelwas used as base materials, CO₂ laser was used to form composite coatingswith thickness of 0.1-2.0 mm on failure blades （2Cr13 martensite stainlesssteel） by laser remanufacture technology （laser cladding and laseralloying）.The effect of laser process parameters on microstructures and shapecharacteristics of remanufactured coatings were researched. The residualstress, electrochemical corrosion, wear and cavitations were performed tounderstand the properties of remanufactured coatings. The results showedthat through laser remanufacturing technique, the layer was dense, homogenous, without any pores, crack and slag. The averagemicro-hardness of surface was 737 HV_0.2 and the microhardness of crosssection from laser remanufacturing coatings to matrix was changedtremendously from 768 to 250HV_0.2 (while the hardness of matrix is200-250HV_0.2). The residual stress on surface after laser remanufacturing istensile stress, but it can prevent crack to occur and expand because of denseorganizational, moderate micro-hardness, and dispersed carbide of thesurface. Therefore, although the surface is residual tensile stress, it will notreduce the life expectancy of steam turbine blades. The corrosion potentialand the remain passive current of laser remanufacturing layer are all higherthan the substrate, which means that the electrochemical corrosionresistance is higher than the substrate. The wear resistance and cavitationresistance of the treated blades were doubled to that of the untreated one.Therefore, the laser remanufacturing technique may be applied moreextensively in the failure turbine blades with its high flexibility, stronglycontrollable performance and free of pollution.