Simulation Study On The Deposition Behavior Of Cold Sprayed Aluminum Matrix Composite Coatings

In the process of cold spraying,the sprayed particles are accelerated to a high speed（300-1000m/s）and hit the substrate at a temperature much lower than the melting point of the sprayed material,resulting in a violent deformation to form the coating,which can solve the defects of material oxidation,phase change and grain growth in the process of thermal spraying.By using cold spraying to prepare aluminum coating has better corrosion,dense degree,and not easy to be oxidized,but this method can not change the aluminum coating itself exists some shortcomings,such as low hardness,high porosity,poor dense degree.In order to solve this drawback,we try to add appropriate amount of Al₂O₃ to cold spray aluminum to form a composite coating,and compress the aluminum coating to enhance the denseness and reduce the porosity of the coating.Since the high-speed collision of particles occurs in a short period of time,the deformation behavior of the particles during the collision process cannot be observed step by step in the experimental process.The subject simulates the deformation process of Al-Al₂O₃ composite particle deposition by means of finite element numerical simulation,and analyzes the influence of the initial velocity of particles and preheating temperature on the deposition behavior of particles.Research shows that increasing the initial velocity and preheating temperature of spray particles can help improve the integration of coating and substrate,decreases the porosity of the coating and increases the density of the coating.During particle deposition,the deformation behavior of the particles is mainly influenced by plastic deformation due to impact and the softening effect of temperature rise.When the initial speed and preheating temperature are 350 m/s and 500℃,respectively,the quality of the coating formed by multiple Al particles reaches the best,with particle compressibility of 77.4%,coating porosity of 1.656%,and the temperature of some areas of the underlying particles can reach 584.61℃,close to the melting point of Al material.In order to improve the shortcomings of poor compactness and high porosity of Al coatings,Al₂O₃ particles were added as a hard phase to incident particles,simulation analysis of the effect of different Al₂O₃ content and size on coating properties.As the Al₂O₃ particle content increases from 0%to 25%,the porosity of the coating decreases from 1.656%to 0.672%.When the particle size of Al₂O₃ increases from 15μm increases to 30μm,and the compression ratio of the underlying particles increases from 0.875 to 0.93.In addition,when the impact pressure on Al₂O₃ particles reaches a certain level,damage and fragmentation will occur.The results of the numerical simulation can be coupled to the non-linear relationship between the degree of damage of Al₂O₃ particles and the initial velocity of the particles as well as the preheating temperature.Through this relationship,the crushing behavior of Al₂O₃ particles during deposition can be controlled,so the damage equation obtained from this simulation has some guidance for experiments.