1. Thermal spraying Thermal spraying is a method of using heat source to heat spraying materials, atomizing, spraying and depositing molten or near-molten particles onto the surface of the substrate to form a special surface layer. At present, there are three kinds of heat sources used for spraying; The first is the arc heat source, the second is the plasma flame heat source, and the third is the natural gas heat source. The thermal spraying methods can be divided into arc spraying, plasma spraying and flame spraying. 2. Spray welding (or spray welding) Spray welding is a method of using heat source to heat the material, spray it onto the surface of the base material, and then melt it onto the surface of the base material to form a special surface layer. At present, the main heat source used in spray welding is oxyacetylene flame.