Study On Repairing Process,Microstructure And Mechanical Properties Of 316L Stainless Steel By Laser Addictive Manufacture

Due to the harsh working environment in the nuclear power field,the damage rate of parts is too high.In order to extend the service time of components and reduce the loss,the remanufacturing and maintaining of main materials in the field of nuclear power is the primary task to ensure its safety and long-term operation.In this dissertation,the optimized processing parameters of 316 L stainless steel plate repaired by laser direct deposition technology has been studied.In addition,the comprehensive performance of the repaired specimens has been investigated.The influence of two different 316 L stainless steel commercial powders on performance of the repaired specimens also has been discussed.The main research work is listed as followed:(1)Laser metal deposition was used to repair grooves on 20 mm thickness 316 L stainless steel plates.Based on the orthogonal test design,the cross-section morphology of the restoration was analyzed and the process parameters were optimized.Thus,Good comprehensive performance of fine metallurgical bonding with were successfully achieved under optimized processing parameters.(2)The microstructure and phase composition of the repaired specimens repaired with two common commercial 316 L powder were investigated.Results indicate that the microstructure of the specimens repaired with Fe-0.15C-11.8Cr-0.15Mn-0.2Ni-0.031P-0.56Si-0.05S(wt.%)powder was homogeneous cellular dendrite and consisted of Cr-rich martensite,while a number of fine equiaxed grains were presented in microstructure of specimens repaired with Fe-0.09C-17.05Cr-1.2Mn-11.28Ni-0.019P-0.46Si-0.09S(wt.%)powder and the repaired specimens consisted of ferrite and austenite.(3)The mechanical properties of the repaired specimens with two common commercial 316 L powder(micro-hardness,ultimate tensile strength,bending strength,low-temperature impact toughness)have also been studied.Due to solid solution strengthening,the average hardness of the specimens repaired with former powder was higher than that of the specimens with later powder.However,in the aspect of mechanical properties,laser metal deposition with Fe-0.09C-17.05Cr-1.2Mn-11.28Ni-0.019P-0.46Si-0.09S(wt.%)powder had better performance than the specimens repaired with another kind of powder.(4)Corrosion resistance(corrosive voltage,corrosive current,corrosion rate and morphology)of the specimens repaired with two common commercial 316 L powder has been investigated.The result indicates that the repaired specimens with Fe-0.09C-17.05Cr-1.2Mn-11.28Ni-0.019P-0.46Si-0.09S(wt.%)have better corrosion resistance.In a word,chemical composition(different element contents)of the powders played an important role in determining the microstructure,phases and properties of the specimens.