Experimental Study On Corrosion Resistance Properties Of Laser Cladding Nickel-Based Alloy

In this paper,the corrosion factors of the sucker rod in service environment are summarized,and the laser cladding technology is used to improve the corrosion resistance of the sucker rod.Hastelloy C22 cladding layer and SUS630 stainless steel cladding layer were prepared on 30CrMoA steel.The phase composition,structure and element distribution of the cladding layers were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM)and energy dispersive spectrometer(EDS)respectively.The self-corrosion potential,self-corrosion current density and open circuit potential of the cladding layers in 3.5%NaCl solution and high-chloride brine(NaCl concentration is 218g/L,pH=6)were obtained by electrochemical polarization curve test and open circuit potential test;The change of corrosion resistance of the cladding layers with immersion time was measured by electrochemical impedance method;the corrosion resistance of the cladding layers were verified by copper accelerated acetic acid salt spray corrosion experiment;the corrosion of the cladding layers in high-chloride medium was studied by high-chloride brine immersion corrosion experiment;the corrosion resistance of the cladding layers in extreme medium was further studied by 6%FeCl3 immersion corrosion experiment.The results show that the cladding layer of C22 alloy consists of Ni based solid solution formed by Cr,Mo,Fe and Ni.Mo element in the microstructure is segregated at the grain boundary.The cladding layer of 630 stainless steel consists of martensitic phase and Cr7C3.Electrochemical polarization curve and open circuit potential test results show that the passivation platform of 630 stainless steel cladding layer disappears in high-chloride brine,while C22 alloy cladding layer still maintains a good passivation ability under this condition.The salt spray test results show that the corrosion resistance of C22 alloy cladding layer is much higher than that of 630 stainless steel cladding layer and 30CrMoA matrix steel.After immersion in high-chloride brine for 9 days,C22 alloy coating can still maintain a stable passivation state,and the surface is in good condition after the end of the experiment.However,the corrosion resistance of 630 stainless steel gradually decreases with the extension of immersion time,and finally corrosive pitting occurs.During the corrosion process in 6%FeCl3 solution,corrosive pitting occurred in C22 alloy cladding layer,and the pitting diameter gradually expanded from 20μm to 50μm or even 170μm.After the cladding layer of 630 stainless steel was immersed in 6%FeCl3 solution,cracks appeared on the surface,which was related to the double influences of internal stress and corrosion medium.