Flame spraying refers to the use of the high temperature of the gas combustion flame to melt the spray material (wire or powder) and spray it with a compressed air stream to form a coating on the surface of the workpiece.
As a new type of surface protection and surface strengthening process, flame spraying technology has developed rapidly in the past 20 years and has become a very active branch in the field of metal surface engineering. With the flame as the heat source, the metal and non-metal materials are heated to a molten state, formed into a mist under the impetus of high-speed airflow, and sprayed on the substrate. When the ejected tiny molten particles hit the substrate, they plastically deform and stack up in flakes.
Flame spraying uses fuel gas acetylene, propane, methyl acetylene propadiene (MPS), hydrogen or natural gas, and combustion-supporting gas oxygen as heat sources. The spray material enters the flame through a certain transmission method and is heated to a molten or softened state. Then, it is sprayed onto the substrate by means of gas or flame acceleration. According to the different spraying materials, it can be divided into wire flame spraying and powder flame spraying.
The wire is conveyed by the rotation of the air turbine or motor in the spray gun, the speed of which can be adjusted to control the wire feeding speed. Using the air turbine spray gun, it is difficult to fine-tune the wire feeding speed, and its speed is difficult to be constant due to the influence of compressed air, but the spray gun is light in weight, suitable for manual operation; The adjustment can also be kept constant, and the spraying automation is high, but the heavy spray gun is only suitable for mechanical spraying.
The flame spraying efficiency of wire material is high, but the size of the sprayed droplets is uneven, which makes the coating structure uneven, the porosity is also large, and the forming process of the wire drawing spraying material is limited.
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