[China Aluminum Network] Cold spray is a budding solid-state process. This method can convert the kinetic energy of the ultrasound-accelerated solid particles into heat energy when they hit the surface of the plated part, thereby completing the metallurgical welding. The principle of the process is that each metal has its own specific, temperature-dependent critical particle velocity, which will be welded to the plating when the particle moves beyond this velocity.
In the traditional thermal spraying process, due to the high temperature, both the coating and the plating material are oxidized, resulting in metallurgical deformation and residual tensile stress. On the contrary, the coating made by cold spray process has a very low porosity (<0.5%), and it is also resistant to oxidation and phase change. It can reduce the tensile stress for various metals, cermets or other material combinations.
In high pressure cold spray technology, high pressure helium or nitrogen (350 to 450 psi) is used as a carrier gas to accelerate the spray material to ultrasonic velocity. The gas is heated and forced through a focus-spray nozzle (deLaval), where it is accelerated to ultrasonic velocity (greater than 1000 m/sec). The sprayed particles are injected axially upstream of the spray head. In the low pressure cold spray technique, nitrogen or air is pressurized to 70 to 15 pounds per square inch, and the spray powder is injected radially in the downstream of the divergent portion of the spray head. The low-pressure cold spray system is portable and economical to operate, with particle speeds of up to 800 m/s. The portable cold sprayer can be used to spray aluminum, copper, zinc and other metal combinations. The portability makes the low pressure cold sprayer more suitable for field maintenance and repair.
Cold spraying technology is an effective method to generate a thick aluminum coating on the surface of magnesium alloys. This method does not require high surface preparation and does not need to take into account the mechanical or thermal properties of the coating. The aluminum coating exhibits the ability to prevent various and electrolytic corrosion of magnesium components. In many cases, battery corrosion protection is required only around steel fasteners, and cold spraying is precisely an innovative technique for the partial protection of exposed magnesium surfaces. However, in order to understand and improve the cold spray process, it is necessary to carry out more thorough research, especially for the continuous development and innovation of various material combinations and the cold spray process itself, as well as the better use of materials for future technologies. jobs.

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