Thermal spraying is a surface strengthening technology that uses a certain heat source (such as electric arc, plasma spraying, or combustion flame) to heat powdery or filiform metal or non-metallic materials to a molten or semi molten state, and then sprays them onto the pretreated substrate surface with the aid of the flame itself or compressed air at a certain speed to form a surface coating with various functions.
Different from traditional thermal spraying methods based on heat sources, they can be divided into combustion method and electrothermal method. The former includes flame spraying and explosive spraying, while the latter includes arc spraying and plasma spraying. In recent years, with the further improvement of coating performance requirements, a large number of scientific workers have developed supersonic flame spraying and supersonic plasma spraying on the original basis through continuous innovation. At the same time, processes such as laser spraying, reactive thermal spraying, and cold spraying have been developed successively.
3、 Technological Process
The main technological process of thermal spraying processing: First, the spraying material is heated and melted, and the melted droplets are atomized. After spraying, the particles fly at high speed, and the coating is formed by spraying onto the substrate. During this process, the higher the temperature of the heat source, the greater the impact velocity of the droplet, and the higher the compactness of the coating formed.
4、 Development trend
With the continuous development of industrial machinery, thermal spraying surface strengthening technology plays an increasingly prominent role in repairing corrosion and wear on the surface of workpieces. This not only enhances the surface strength of workpieces, improves their service life, but also improves economic benefits, and is widely used in various industries. For example: ⑴ Large area long-term protection technology has been widely used in folding. ⑵ Repair and strengthen the localization of large equipment and imported components. ⑶ Application of supersonic flame spraying technology. ⑷ Gas deflagration spraying technology has been further applied (5)The technology of oxyacetylene flame plastic powder spraying has developed rapidly(6)Thermal spraying technology has been applied in chemical anti-corrosion engineering (7)Laser remelting technology began to be applied (8)It has also been applied in building decoration, medical and health care.
The relevant metals used for thermal spraying processes mainly include 316L, 304L, H13, 17-4PH, 18Ni300, etc.
The physical and electron micrographs of some metal powders are shown below (Changsha TIJO Metal Materials Co., Ltd.)
Brand:316L water atomized stainless steel powder
Features: Good appearance gloss, excellent corrosion resistance, excellent high-temperature strength, excellent work hardening, and good welding performance
Purposes: Thermal spray soldering, PM powder metallurgy process, aerospace and marine materials, stainless steel medical devices, stainless steel porous materials, etc
Brand:18Ni300 maraging steel powder
Features: High strength and hardness, good toughness and plasticity, high strength and toughness, high yield strength ratio, and good machinability
Purposes: Widely used in aviation, aerospace, precision mold, military industry, and other fields