Analysis on Organization and Properties of Laser Clad Inconel625 Coating on 304 Stainless Steel Surface
Laser cladding technology has many advantages over traditional surface modification methods,including complete metallurgical bonding,low heat input process,small heat-affected zone,low dilution rate,high solidification rate,and the ability to prepare thin and light coatings. Therefore,in order to improve the surface modification of stainless steel parts and improve the wear and corrosion resistance of stainless steel parts in cogeneration plants due to the waste of resources and equipment scrap caused by corrosion and wear,laser cladding was used to improve the wear and corrosion resistance of stainless steel parts. The laser cladding technology was used to prepare Inconel625 coating on the surface of 304 stainless steel. Industrial microscope,scanning electron microscope,X-ray diffractometer,ultra-depth of field instrumentation and other equipment were used to systematically explore the surface morphology of the cladding layer,microstructure,elemental distribution,and surface roughness. Microhardness tester,friction and wear equipment,electrochemical workstation and other equipment were used to test the hardness distribution pattern,wear and corrosion resistance of the fused cladding layer. In the single-factor test,the minimum dilution rate and the best macroscopic appearance were taken as the optimization basis,which led to the optimal process parameters of laser power 1200 W,powder feeding rate 10 g/min,scanning speed 14 mm/s. The bottom to top organization of the fused cladding layer with optimal parameters was mainly dominated by typical dendritic crystal organizations with different morphologies,as well as a small amount of cytosolic crystals. The physical phases mainly consisted of FeCr0.29Ni0.16C0.06,NbC,Cr2Ni3,Mo2C,etc. Compared with the substrate,the coating hardness was greatly improved,the highest hardness value of the coating reached 425.48HV0.2,which was about 1.8 times the substrate. The main reason was due to the rapid heating and cooling process,resulting in the surface organization of the nuclei to grow. Compared with the coating,the internal organization was more uniform and denser,resulting in higher hardness in the upper and middle parts of the layer. The hardness of the upper and middle parts of the fusion-coated layer was higher,and the hardness of the heat-affected zone was lower. The wear amount of the coating was 2.4 mg,which was about 55％ of the substrate wear amount of 4.4 mg. The friction coefficient was smooth,the magnitude of change was small. Compared with the substrate,its wear resistance was significantly improved;This was mainly because the fusion cladding layer in the organization contained a relatively small dense dendritic crystal structure,and had a more rigid phase components,could significantly attenuate the wear in the plastic deformation,reduce the degree of wear and reduce friction scratch,and increase the surface strength and hardness of the coating. The hardness was lower in the heat affected zone. So that the surface strength,hardness increases,and wear of the coating was reduced,and the wear resistance was improved. After the electrochemical corrosion test,the open-circuit potential of the substrate was-0.44 V,the open-circuit potential of the fusion-coated layer was stabilized at-0.17 V,which was more positive than that of the substrate,and the self-corrosion potential (Ecorr) of the coating was-1.00 V,which was greater than that of the substrate-1.10 V,and the self-corrosion current density (Jcorr) of the coating was 3.47×10-8 A/cm2,which was less than that of the substrate,and the self-corrosion current density of the coating. The self-corrosion current density of the coating was 3.47×10-8 A/cm2,which was less than that of the substrate of 6.43×10-8 A/cm2,which led to the conclusion that the corrosion tendency of the coating was smaller than that of the substrate,the capacitive arc radius of the coating was larger than that of the substrate,and the impedance modulus of the coating was larger than that of the substrate in the frequency range,which indicated that the coating was more corrosion resistant. In conclusion,Inconel625 alloy coating can significantly improve the surface hardness,wear resistance and corrosion resistance of 304 stainless steel.
laser claddingmicrostructuremicrohardness304 stainless steelgalvanic corrosionfriction and wear test
万方数据
维普
