What is the technology of plasma spraying?

Plasma spraying technology is a surface treatment process developed in the 1950s. Plasma spraying equipment and process involve selecting a plasma arc generator (spray gun) to heat and ionize gases such as Ar and N through a nozzle (commonly used), forming a high-temperature and high-speed plasma jet, melting and atomizing metal or non-metal materials, and spraying them at high speed onto the surface of the pre treated workpiece to form a coating.

Plasma spraying is a material surface strengthening and modification technology, which has the advantages of wear resistance, corrosion resistance, high temperature oxidation resistance, electrical insulation, and material surface strengthening and modification technology. Using DC driven plasma spraying technology, materials such as ceramics, alloys, and metals are heated to a molten or semi molten state and sprayed at high speed onto the surface of the workpiece to form a sturdy surface. Spray a layer of several tens of microns onto the surface of artificial bone to enhance its affinity and affinity. The parameters of the spray gun mainly include the composition and flow rate of the working gas, electrical parameters, powder feeding rate, spray distance and angle, and the relative motion speed between the spray gun and the workpiece.

The plasma spraying process is suitable for spraying refractory materials. The plasma spraying speed is high, which can reach tens to hundreds of meters per second. Therefore, the bonding strength between the coating and the substrate is high, the coating is delicate, and it has little thermal impact on the substrate. The spraying process specification for the appearance of formed workpieces is stable, easy to operate, and has high spraying power. At present, plasma spraying technology is used to prepare ceramic surfaces and metal transition layers for thermal barrier coatings. There are several plasma spraying processes classified according to different spraying environments, including atmospheric plasma spraying (APS), maintenance atmosphere (argon) plasma spraying (ASPS), low-pressure (LPPS) or vacuum plasma spraying (VPS).

Post treatment of coatings

1. It's a sealing treatment. To prevent corrosive media from reaching the substrate through the coating holes, the coating should be sealed. There are many materials that can be used as sealing agents. It is feasible to select appropriate sealing agents, such as workpiece quality, environment, temperature, cost, etc.

For workpieces subjected to high stress loads or impact wear, the spray coating needs to be remelted (such as flame remelting) to improve the combined strength of the coating Induction remelting Laser remelting Hot static pressure, etc. The dense coating that is metallurgically bonded to the substrate is formed by a porous coating that is only mechanically bonded to the substrate.

3. If there is a requirement for dimensional accuracy, mechanical processing should be used. Because spray coatings have characteristics different from general metal and ceramic materials, in order to ensure the smooth progress of spray mechanical processing and the required dimensional accuracy, it is necessary to choose a reasonable processing method and corresponding process parameters.