Study On TiC/Ni Composite Coating By Laser Cladding On Aluminum Alloy Surface And Its Properties

There are many advantages of aluminum alloy such as high specific rigidity and specific strength,good corrosion resistance,easy forming and processing,etc.It is widely used in various fields such as transportation,construction engineering,aerospace,electronic communication and so on.However,its disadvantages of low hardness,poor wear resistance,and poor heat resistance limit its application under special conditions such as wear and high temperature,for example,engine cylinders,pistons,missile shells and so on.This subject intends to prepare high hardness and high wear resistance TiC/Ni composite coating on the surface of ZL101 aluminum alloy by laser cladding technology,so as to effectively improve the surface performance of aluminum alloy materials.In this paper,in order to solve the problems of poor coating adhesion and surface cracks during the laser cladding process on the aluminum alloy surface,a step-by-step cladding study by adding a transition layer was carried out.The material of the transition layer and the application process of the transition layer were determined.The single-layer and multi-layer laser cladding processes of the nickel-based composite coating were investigated,and a nickel-based composite coating with good bonding performance,smooth surface and no cracks was prepared.The performance of the nickel-based composite coating was evaluated.The research content of the paper mainly included:（1）when laser cladding TiC/Ni composite coatings on the surface of ZL101aluminum alloy,it was difficult to obtain a cladding layer that combined well with the substrate.Under different laser process parameters,the cladding layer was almost completely detached from the substrate.In this project,Cu64Ni18Zn18 alloy was selected as the transition layer material.With the help of finite element simulation method,the influence of the addition of copper-based transition layer on the temperature and stress fields during laser cladding was analyzed,and the laser cladding process parameters were optimized.The simulation analysis results showed that adding the copper-based transition layer under the same laser parameters increased the maximum temperature of the bottom of the nickel-based cladding layer by 6%and the temperature of the center of the molten pool by 2.4%.The increase in the temperature of the molten pool was conducive to the full melting of the material in the cladding area and the molding quality of the cladding layer was improved.In addition,the addition of a copper-based alloy transition layer could reduce the residual stress value at the joint surface of the cladding layer and the substrate,thereby reducing the crack sensitivity of the cladding layer.A step-by-step cladding process was used to prepare a TiC/Ni composite coating with a copper-based alloy transition layer.The results showed that a cladding layer that combined well with the substrate can be obtained.（2）Using the response surface optimization method,with full melting of the cladding layer,improving processing efficiency and reducing energy consumption as the optimization goals,through a single-channel laser cladding simulation simulation analysis,the process parameter combination was initially determined as:laser power427W,defocusing amount 14mm,The scanning speed is 5mm/s,which provided guidance for the subsequent laser cladding experiment.Based on the simulation results,single-channel and multi-channel laser cladding process optimization experiments were carried out.The obtained process parameter combination was:laser power 500W,defocusing amount 10mm,feed speed 4mm/s,pulse width×frequency8ms×6Hz,transition The thickness of the layer was 0.15mm and the multi-channel overlap rate is 50%.There were still a few cracks in the cladding layer prepared by this process parameter.Further remelting the cladding layer could obtain a cladding layer with a smooth surface and no cracks.（3）The research showed that the composite cladding layer prepared by the above process formed a good metallurgical bond between the nickel-based composite coating and the transition layer,and between the transition layer and the aluminum alloy substrate.There was a hard cladding layer of about 0.4mm on the surface of the aluminum alloy workpiece,and the hardness reached 800HV_0.3,which was about 13times higher than that of the substrate.Comparing the wear resistance of the ZL101aluminum alloy substrate and the nickel-based composite coating,it was found that the wear resistance of the nickel-based composite coating is significantly improved compared to the substrate.