The powder is injected into the spray gun, and oxygen-acetylene mixture is introduced at the same time. The detonating gas is ignited to produce a high temperature of 3300℃. The powder is heated and sprayed onto the surface of the workpiece at a speed of more than 2 times the speed of sound, forming a high bonding strength and high bonding strength with a diameter of -20mm and a thickness of -8μm Dense coating. The entire coating is formed by overlapping small circular flakes.
(1) Explosive spraying of 0.25 mn thick WC on the aero-engine ferroalloy fan blade damping table increases the service life by 10 times:
(2) A layer of 0.12mm thick Cr3C2 is sprayed on the positioning snap ring of the combustion chamber, which increases the service life by 7 times.
(3) At present, explosive spraying is mainly used to prepare high-quality wear-resistant coatings.
The fuel gas (hydrogen, propane, propylene or MAPP) and the combustion-supporting agent are introduced into the combustion chamber in a certain proportion and mixed and burned explosively. The high-temperature gas enters the copper nozzle through the four inclined nozzles in the upper combustion head of the combustion chamber, and the powder is fed by the powder Gas (Ar or N2) is quantitatively sent into the high temperature gas along the carbide center sleeve in the combustion head, and the high temperature and high speed gas is taken out of the nozzle, and the high speed nozzle forms a coating on the workpiece. The entire spray gun is cooled by circulating water.
90s: laser cladding technology
my country's thermal spraying technology started in the 1950s, when Wu Jianchun and Zhang Guanbao established the first domestic professional spraying plant in Shanghai, developed oxygen block flame wire spray and electric spray equipment, and developed metal spraying business externally. my country's thermal spraying technology started earlier, and wire arc spraying was developed in the 1950s; some military departments began to study plasma spraying in the 1960s: in the 1970s, spraying equipment and materials with a complete range of varieties and models appeared, but overall progress Slow, only in recent years has it achieved rapid development.
The characteristics of thermal spraying technology: the application of thermal spraying technology has been developed from the preparation of decorative coatings to the preparation of various functional coatings, such as wear resistance, corrosion resistance, oxidation resistance, heat insulation, conductivity, insulation, friction reduction, and lubrication , Anti-radiation and other coatings. Thermal spraying can be used for both repair and manufacturing. Since the performance of the coating material is better than that of the substrate, the surface of the part can be coated with it, which can greatly improve the quality of the product.
Selection of coating materials:
(1) The thermal spraying material preferably has a wider liquid phase zone, which can keep the droplets of the coating material in the liquid phase for a long time.
(2) Good thermal stability, no sublimation or decomposition in high temperature flame flow. If the material is easily decomposed at the temperature of thermal spraying, it is not suitable for thermal spraying.
(3) The spray material should have good wettability with the substrate in the molten state to ensure good bonding performance between the coating and the substrate.
(4) The thermal expansion coefficient is similar to that of the base material to prevent large thermal stress from being caused by the large difference in the expansion coefficient.
Coating formation process:
(1) The spray material is heated to a molten state.
(2) The sprayed material is atomized into tiny droplets and hits the surface of the substrate at high speed. The greater the kinetic energy and the greater the impact deformation of the particles that strike the substrate, the better the combination of the coating.
(3) The molten high-speed particles deform after impacting the surface of the substrate, and form a coating after condensation.
Thermal spraying has become an important method for the preparation of wear-resistant coatings and is widely used in various national economic fields. The porous layered structure of the coating makes its wear-resistant service behavior significantly different from that of similar blocks. The most important feature is the load influences. Under low-stress service conditions, thermal spray coatings show good wear resistance, but when the stress is higher than a certain level, due to the accelerated propagation of cracks along the interface of the deposited particles and accelerated wear, especially in erosion and cavitation erosion Under the conditions of, fretting, fatigue, and abrasive wear, the potential of the coating material can only play 10%-30%. Therefore, the establishment of basic research on the systematic relationship between the coating structure, performance, service conditions, and service efficiency, and the establishment of a database to guide the design and use of wear-resistant coatings, will be to give full play to the material potential and improve the service of thermal spray coatings. Effectiveness, an important way to save resources and energy.
