Research On Preparation Technology And Performance Of Ni-based Coating On Copper Alloy Surface

Copper alloy is widely used in various industrial fields because of its excellent thermal conductivity,electrical conductivity and corrosion resistance.Under the extreme conditions of long-term work,copper alloy is prone to wear and corrosion failure,and the failure of copper alloy will cause huge economic losses to the production and manufacturing of engineering.In order to avoid the failure behavior of copper alloy,high performance coating is mainly prepared on copper alloy by suitable surface treatment technology to improve the performance and service life of copper alloy products.Laser cladding coating is one of the main methods for surface modification of copper alloy.However,due to the high thermal conductivity and reflectivity of copper alloy,and the influence of laser cladding process parameters and powder composition,it is difficult to prepare high-quality coating by laser cladding coating.Therefore,in this paper,aiming at the poor wear resistance and corrosion resistance of copper alloy in long-term use,the Ni-based alloy coatings with different preheating temperatures and compositions were prepared by using the finite element theory and response surface method with reasonable laser melting coating process parameters.The macro morphology,phase,microstructure and properties of the coatings were analyzed.The specific research contents of this paper are as follows:Firstly,based on the finite element theory,the numerical simulation of the single-channel laser cladding process of copper alloy is carried out.Through the temperature field of laser cladding coating and substrate,the thermal cycle characteristics of laser cladding coating were analyzed and compared with the experimental results.The depth of molten pool prepared by laser is about 0.76mm and the width of cladding coating is about 1.53mm,which are basically consistent with the simulation results of laser cladding coating.At the same time,the effects of cooling rate,temperature gradient and solidification rate on the microstructure of cladding coating were analyzed,and the microstructure of Ni-based alloy was revealed.Secondly,taking laser power,scanning speed and preheating temperature as input factors,three levels were designed for each factor,and the coating height,depth and hardness were taken as target responses.The process factor optimization experiment was designed based on Box-Behnken response surface method.The second-order model between target response and input factors is established to analyze the influence of input factors on height,depth and hardness.The analysis of the prediction model shows that the laser power is the most significant factor affecting the coating height and hardness,and the preheating temperature is the most significant parameter affecting the coating depth.The coating was prepared on the surface of copper alloy by obtaining the optimal process parameters,and the coating was preliminarily analyzed.Thirdly,taking the preheating temperature of copper substrate as the research object,the laser melting experiments of 100,200,300 and 400°C preheating temperature were designed,and the experimental results were analyzed.The macroscopic morphology,microstructure and phase composition of the coatings with different preheating temperatures were observed,and the hardness,friction and wear properties and corrosion resistance of the coatings were analyzed.The causes and microstructure evolution of defects in the coatings with different preheating temperatures were revealed.The results show that the coating with 200°C preheating temperature has the best wear resistance and corrosion resistance.Finally,by designing Ni-based alloy powders with different WC compositions（5,10,15 and20%）,four kinds of coatings were prepared by laser melting coating.The macro morphology,microstructure and mechanical properties of the coatings were analyzed.The results show that 20%WC has the maximum microhardness(1419 HV_0.5),and the wear rates of the four coatings are respectively...