The Analysis On The Particles’ Acceleration Performance And Deposition Mechanism In The Cold-gas Dynamic Spraying Processes

Cold gas dynamic spraying technology(referred to as the cold spray) is a coatings fabrication technique based on the aerodynamics principle. Compared with thermal spraying, the cold spray has the characteristic of anti-oxidation, and can improve deposition rate,has the advantages of small residual stress, so the cold spraying is getting the attention of scholars at home and abroad. The process of cold spray process consists of particles’ acceleration in the nozzle flow field and the particles’ on the substrate collision deposition. Because of the complexity of the process, many factors have influences on the coating deposition. Therefore, the analysis of flow field in the nozzle has important meaning for studying the particles’ acceleration performance in the nozzle flow field and particles’ deposition mechanism on the substrate, and that can provide a theoretical basis for experimental study.Firstly, the numerical simulation analysis of the nozzle is carried on using the software Fluent in this paper. Nozzle’s two-dimensional physical mode is established, and then analyzing the effect of different spray temperature and spray pressure have on flow field and temperature field, and also considering the effect of different gas carriers, particle materials, particle sizes and particles’ launch position have on particles’ acceleration performance. Then, the processes that particles are depositing into substrate are simulated using finite element analysis software ANSYS, and analyzing the effect of different particle’s launch speed, launch angle, materials, size and substrate materials have on the deposition and plastic deformation. Then two-deposition and deposition performance of multi-particle swarm are analyzed. The main conclusions are as follows:(1)The velocity of the flow fluid increases gradually as the spray temperature increasing; But the spray pressure has little effect on flow field and temperature field of a nozzle.(2)He as a gas carrier has better performance for particles’ acceleration performance than N2. The larger particle diameters, the earlier particles gaining speed due to their inertia. But when the particle diameters is less than 1μm, they have unstable movement because of the susceptible to gas. The lower density, the greater speed can obtain regardless of metal or nonmetal particles.(3)The launch position of particles in the entrance of a nozzle has small effect on velocity, but it has an impact on particles’ angle of colliding substrate. Increasing particles’ speed and launch angle are beneficial to particle deposition, but launch angle should be less than 200. The yield limit of material has an important influence on the particle deposition.(4)Particles of micron size are more easily to form coating than nanometer, and the particles size 20μm have better coating performance than 10μm and 40μm.(5)It is the level interaction between particles that makes gap exist between particles and substrate, and the vertical interaction that has no affect on the depth of dimples in substrate can play a role in compacting around. The multi-particle swarm’s deposition increases metal lasing phenomenon around the contact area.