Powder morphology: spherical aluminum powder, see Figure 1
The main purpose:
1) The coating of aluminum powder spraying is non-magnetic, relatively soft and ductile, has good electrical conductivity and thermal conductivity, has good radio wave shielding ability and anti-shock resistance, and can be used for radio frequency shielding coating.
2) Although the aluminum coating has good environmental corrosion resistance, it is rarely used to spray the corrosion-resistant coating with aluminum powder. In coastal and industrial atmospheric conditions, for corrosion applications on large structures, aluminum wire arc spray coatings are often preferred over powder spray due to the portability and ease of use of the equipment.
3) For repairing aluminum and magnesium alloy parts.
Spraying method: Aluminum has a strong affinity for oxygen, and powdered aluminum has a huge surface area. In order to reduce the oxide content of the coating, low pressure plasma spraying or protective atmosphere plasma spraying is usually used. When spraying with a combustion gas flame, a weak carbonizing flame should be used. The coating is best prepared by the cold spray method.
Coating properties:
Using plasma spraying, the bonding strength can reach 20MPa, the surface roughness is 12.5–25µm, the coating hardness is 80–90 HR15Y or 33–45HV0.3, and the porosity is 5–10vol.%.
Using cold spraying, the bonding strength can reach more than 40MPa, and the porosity is 1-3vol.%.
Note: Pure aluminum powder cannot be sprayed by cold spraying, and a certain proportion of alumina powder needs to be mixed with pure aluminum powder.
