3. High-speed flame spraying
The principle of high-speed flame spraying is to introduce fuel gas (hydrogen, propane, etc.) and combustion-supporting agent (O2) into the combustion chamber in a certain proportion, mix them, and then burn explosively to produce high-temperature and high-pressure combustion gas. The high-temperature gas produced by the combustion passes through the expansion tube at high speed to form a high-temperature and high-pressure supersonic flame flow. At the same time, the powder feeding system feeds the powder material from the low-pressure area into the flame flow, and after heating and acceleration, it is sprayed onto the surface of the workpiece to form a coating.


The working temperature of high-speed flame spraying is relatively low, the heating temperature of the powder is low, the movement speed is high, the oxidation of the spraying material is relatively light, the surface roughness of the obtained coating is small, and the coating bonding strength and density are high. Therefore, high-speed flame spraying is suitable for the preparation of metal and low-melting-point nano-ceramic coatings. At present, high-speed flame spraying is the most commonly used method for preparing WC-Co nanostructured coatings.