Definition of Thermal Spray

       Thermal spraying is to use a heat source to heat the sprayed material to a molten or semi-melted state, and rely on the heat source's own power or an external compressed air flow to atomize or push the molten particles into a sprayed beam, which is sprayed at a certain speed to the pretreated. The process method of forming a coating on the surface of the workpiece.



Features of thermal spray:



Thermal spraying technology has two prominent features: one is that the composition of the sprayed powder is not limited and can be selected according to special requirements; the other is that the temperature of the workpiece can be controlled during the thermal spraying process, thereby reducing deformation, oxidation and phase change, etc., so that the material itself The performance of the thermal spray coating is not destroyed or lost. These characteristics and the special functions of thermal spray coating such as heat resistance, corrosion resistance, wear resistance, oxidation resistance, insulation and heat insulation have led to the rapid development of thermal spray technology. The economics and technical performance of the coating technology should be considered when choosing a coating technology, the surface coating or other methods of surface modification and treatment should be considered in the entire system, the function required by the surface, the service environment should be known , The performance of the surface treated by the substrate (alloy, heat treatment, etc.) must take into account the technical problems and economics of the coating itself, the service life and advantages of the coating, not just the production cost of the coating.



How to use thermal spray:



Depending on the heat source used in thermal spraying and the state of the sprayed material. Arc spraying is a method in which an arc is generated between two continuously fed metal wires connected to the positive and negative electrodes of the power supply, and the heated molten part is atomized by a compressed air jet and sprayed onto the substrate to form a coating. Since this method is only suitable for spraying wire, it is also called arc wire spraying.



Features:



(1) The spray material must be a conductive material.



(2) The arc temperature is lower than the plasma temperature, but higher than the oxyacetylene flame temperature. The compressed air pressure of the atomized wire can be higher, so the spray layer is denser.



(3) Since the two wires are fed at the same time, the spraying efficiency is high.



2. Uses: It is suitable for spraying of large shafts and rollers and for long-term protection of large structural parts.



How does thermal spraying heat materials:



1. Thermal spraying is a method of using a heat source to heat the sprayed material, atomizing, spraying and depositing the particles in the molten or near-molten state on the surface of the substrate to form a special surface layer. At present, there are three main heat sources used in spraying; one is the arc heat source, the second is the plasma flame heat source, and the third is the natural gas heat source. From this, thermal spraying methods can be divided into three categories: arc spraying, plasma spraying and flame spraying.



2. Spray welding (or spray melting) spray welding is a method of using a heat source to heat the material, spray it onto the surface of the substrate, and then melt it onto the surface of the substrate to form a special surface layer. At this stage, the heat source used in spray welding is mainly oxyacetylene flame.