Research On Technology,Wear And Corrosion Resistance Of Laser Cladding 316L Composite Coating On 45# Steel Surface

Laser cladding technology is a green and advanced metal surface additive technology that commonly used in industry.316L stainless steel is widely used in surface repair and modification of the scrap parts due to its excellent corrosion resistance,mechanical properties,and good compatibility with carbon steel and cast-iron parts.However,there are some problems in its application.such as low hardness and poor wear resistance which could not meet the requirements of parts under high-strength and high-load conditions.At present,there are a few studies on 316L as a melt coating material and even fewer studies on the design of 316L composite powder to improve the wear and corrosion resistance of 45#steel at home and abroad.In this thesis,the LDM2000-60 fiber-coupled laser is used to carry out laser cladding experiments on the surface of 45#steel substrate with different process parameters,from which the best process parameter was selected.The 316L powder is added with different contents of nickel-coated WC particles during the laser cladding experiments to select the optimum addition amount.On this basis,add different content of CeO₂powder to get the best composite powder ratio.The macroscopic morphology,microstructure and SEM-EDS micro-domain composition of the cladding layer were analyzed.Besides,the microhardness,surface wear performance and corrosion resistance of the cladding layer were characterized.Among them,is the influence of process parameters,WC and CeO₂on the cladding layer in the laser cladding process was described respectively,thus the best process and material ratio were selected.The experiment results of the process parameters show that the laser power and scanning speed affect the macroscopic,microstructure and properties of the cladding layer significantly.With the increase of laser power and scanning speed,the surface of the cladding layer is more uniform and smoother.The structure gradually becomes thinner.Moreover,the dilution rate gradually increases and decrease respectively.In addition,with the increase of laser power,the hardness of the cladding layer increases.The friction factor and wear volume firstly decrease and then increase,while the corrosion resistance shows an opposite tendency.Similarly,the scanning speed and the performance of the cladding layer also present corresponding laws.When the laser power is 1.8 k W and the scanning speed is 600 mm/min,the cladding layer shows an optimum comprehensive performance.The experiment results of the WC content study show that:with the increase of WC content,the unmelted WC particles in the cladding layer gradually increase,and the structure of the cladding layer is refined.However,the directionality of dendrite growth is not significant.With the increase of WC content,the hardness of the cladding layer increases,the friction coefficient and wear volume firstly decrease and then increase.,The corrosion also decreases first and then increases.When the content of WC is 15%,the hardness of the cladding layer is 690 HV,which is 2.3 times of the matrix（300 HV）.The minimum friction coefficient is 0.56 and the minimum wear volume is 0.152 mm³,which shows the best wear resistance of three times of 316L cladding layer.The self-corrosion potential is-0.430 V,and the minimum self-corrosion current density is4.066e-6 A/cm²,which is better than 316L cladding layer.Under this condition,the comprehensive performance of the cladding layer is the best.The experiment results of the CeO₂content study show that the addition of CeO₂not only reduces the cracks and pores at the joint,significantly reduces the penetration depth,but also accelerates the melting of WC particles.When the addition amount of CeO₂is no more than,the microstructure of the cladding layer is refined and the secondary dendrite spacing is reduced.However,when the content of CeO₂exceeds 2%,the structure does not continue to be refined,but the primary dendrite become more developed.Compared with the coating without CeO₂,the coating with CeO₂shows an improved hardness,wear resistance,and corrosion resistance,especially the corrosion resistance which is up to 4.2 times higher.With the increase of CeO₂（1%-3%）content,the mechanical properties of the cladding layer also have an optimal value,and the optimal addition amount is 2%.41pictures,17tables,81references.