Including thermal spraying, flame spraying, arc spraying, plasma spraying, explosion spraying and HVOF, their common feature is to arc, flame, plasma or laser as heat source, heating powder to melt or semi molten state, the droplet adhered to the workpiece surface coating. Therefore, there will be some problems such as powder oxidation, phase transformation, decarburization, or change of physical and chemical properties of the original powder during thermal spraying. Meanwhile, it will cause bad thermal effects on the substrate. Even by the cold spray process due to mechanical and electrical, and powder particle deposition is in low temperature, compared with thermal spraying, the biggest advantage is that spray temperature is much lower than all of the thermal spraying process, which has many advantages.
Because cold spraying is the high-speed movement of powder particles on the substrate to achieve deposition, therefore, has many advantages at the same time, cold spraying also has its own shortcomings:
1. it is difficult to deposit brittle material coatings, including brittle ceramic materials and brittle metal materials, which can not be formed by cold spraying.
2. when spraying certain powder particles, expensive He must be used as the carrier gas to obtain high quality coatings.
3., cold spraying can not be diffraction, and can not spray on the surface of complex parts.
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