Heat accumulation behavior and temperature control in thermal spray forming process

       As an important technology for surface strengthening of parts, thermal spraying technology plays an important role in improving the comprehensive performance of parts such as wear resistance, corrosion resistance and high temperature resistance, and prolonging the service life of parts. However, during the thermal spray forming process, the high temperature of the flame and the concentration of energy density can easily lead to the accumulation of a large amount of heat in the coating/substrate system, which in turn leads to thermal cracking or even cracking and peeling of the coating, reducing the service reliability of the coating and shortening the coating. working life.





      Aiming at the problem of coating quality degradation caused by heat accumulation, the current research focus is to explore the heat accumulation behavior of thermal spray forming process and monitor the temperature field of the coating/substrate system, so as to grasp the dynamic change process of the temperature field of the system. According to the heat accumulation law of the system, adjusting the spraying process parameters and loading the cooling medium to realize the temperature control of the coating forming process is an important method to improve the coating forming quality, create a good external environment for the coating forming process, and solve the coating/substrate heat. Cumulative puzzles.





      In recent years, researchers have comprehensively applied numerical simulation and experimental testing methods to explore the heat accumulation behavior of the coating/substrate system during the thermal spray forming process, and to study its temperature evolution law. Based on the characteristics of high efficiency and visual visualization of numerical simulation, the temperature field distribution on the surface and cross-section of the substrate under different spraying distances and different physical parameters of the substrate was studied. On this basis, the influence of different heating trajectories of the dynamic spray gun on the heat accumulation of the system was studied, and the temperature change of the system during the dynamic layer-by-layer lap stacking process was considered. This paper also summarizes the applicability, advantages and disadvantages of various temperature measuring equipment in the temperature measurement of substrate/coating system. Other scholars analyzed the influence of the moving speed and trajectory of the spray gun on the heat accumulation of the system, and tried to control the spraying process to keep the temperature of the system in a suitable range. Based on a comprehensive comparison of the advantages and disadvantages of different cooling media such as compressed air cooling, water cooling and dry ice jet cooling on the temperature control of the system, it is proposed that dry ice cooling has dual functions of cleaning and heat dissipation, which can greatly improve the overall performance of the coating.