Study On Microstructure Regulation And Modification Of Laser Cladding 3%Y₂O₃ Medium Carbon Iron-based Wear-resistant And Corrosion-resistant Alloy Coating

3Cr13 martensitic stainless steel has good strength and toughness and moderate corrosion resistance,and is widely used in pipelines,turbine blades,valve parts and other fields in the oil and gas industry.However,due to its insufficient hardness,it cannot meet the requirements of surface wear resistance.Therefore,the laser cladding technology is used to prepare a 3%Y₂O₃ medium carbon iron base high wear resistance and corrosion resistant coating on the surface of 3Cr13 martensitic stainless steel,in order to obtain a good metallurgical bond with the substrate at a lower cost,similar thermal expansion coefficient,and dilution High-performance coating with low rate,which can effectively increase the service life and application range of engineering parts.In this paper,by adjusting the content of Cr in the medium carbon iron-based alloy powder,the effect of Cr on the structure and performance of the coating was explored;ultrasonic vibration-assisted laser cladding was introduced to improve the dendrite structure;and different heat treatment processes were used to improve the coating Microstructure and carbide morphology,size and distribution in order to obtain a coating with high hardness,wear resistance and corrosion resistance.Through the above research and analysis,the following results and conclusions are obtained:1.Using laser cladding technology to cladding 3Cr13 martensitic stainless steel substrate surface to prepare different Cr element content?nominal mass is 11%¹7%?iron-based alloy coating,analyze the change of Cr element content on the coating structure,hardness and Influence of wear resistance and corrosion resistance.The cladding layer and the substrate have a good metallurgical combination effect.The cladding layer structure is mainly composed of martensite,residual austenite and grain boundary alloy carbide eutectic structure.Carbide types are mainly Fe ₃C,M₅C₂,M₇C₃,M₂₃C₆.As the Cr content increases,it is easier to form high-carbon carbides.The number of primary dendrites and the aspect ratio in the cladding layer decrease,and the number of eutectic carbides gradually increases.When the Cr content is 15%,the average microhardness of the cladding layer is the highest(678.41HV_0.2),which is36.41HV_0.2 higher than the original sample.Compared with the stainless steel substrate,the wear resistance of the coating is significantly improved.With the increase of Cr content,although the self-corrosion potential of the cladding layer decreases,a widened passivation area appears,the pitting potential increases,and the passivation ability is enhanced.It can be seen that increasing the Cr content can improve the material by increasing the surface p assivation ability.Corrosion resistance.At 15%Cr content,the passivation zone is the widest,the pitting potential is the highest,and the coating has the best corrosion resistance.2.By applying ultrasonic vibration of different frequencies to assist laser cladding,after applying ultrasonic vibration,it has little effect on the phase composition of the cladding layer.The structure of the cladding layer is still composed of martensite,residual austenite and grain boundary alloy carbide.However,the coating structure is obviously refined,the pore cracks are reduced,the cell crystal dendrites in the cladding layer are reduced,and the equiaxed crystals are increased.The application of ultrasonic vibration can increase the average microhardness of the cladding layer.The cladding layer has the highest microhardness at an ultrasonic frequency of 20.2kHz,which is 699.81HV_0.2;when the ultrasonic vibration frequency is 20.2kHz,the friction coefficient of the cladding layer decreases a nd the amount of wear decreases,The form of wear is abrasive grain wear,and the scar is shallow,which significantly improves the wear resistance of the cladding layer.Compared with the corrosion resistance of the cladding layer without applying ultrasonic vibration,after applying ultrasonic vibration,the self-corrosion potential of the cladding layer increases,the dimensional passive current density decreases,the stability of the passivation film increases,and the uniform corrosion resistance of the cladding layer improves.When the ultrasonic vibration frequency range is19.8²0.2kHz,the structure of the cladding layer is obviously refined,the hardness and wear resistance are also correspondingly optimal,the corrosion resistance is the best,and the comprehensive performance of the cladding layer is the best.3.The cladding layer samples are modified by different heat treatment processes.At different temperatures of 1050?,the cladding layer structure changes greatly.After heat treatment,the cladding layer structure changes into fine needle-shaped Martensite Body structure,and the dendrites are melted,and granular,short rod-shaped and short rod-shaped precipitates appear in the cladding layer;and the average microhardness of the cladding layer after holding at 1050?for 60 minutes is the highest,which is 718.1HV_0.2;In the subsequent heat treatment,the self-corrosion potential of the cladding layer increases,and the self-corrosion current density decreases.At 30 minutes,the dimensional passivation current of the cladding layer is the lowest,the pitting potential is the largest,and the comprehensive corrosion resistance is the best.It can be seen that a reasonable follow-up heat treatment process is one of the methods for coating surface modification.