Plasma Spray-Coating Technology

Plasma spraying is a thermal spraying method that uses a non-transferable plasma arc as the heat source, with powder as the sprayed material. Commonly used process methods include atmospheric plasma spraying, low-pressure plasma spraying, and solution plasma spraying. Plasma spraying is one of the most important process methods in thermal spraying technology.

Principle:

Atmospheric plasma spraying, commonly referred to as plasma spraying, is achieved through a plasma gun. The nozzle (anode) and electrode (cathode) of the plasma gun are connected to the positive and negative terminals of the power supply, respectively. Working gas is introduced between the nozzle and electrode, and an electric arc is ignited with the help of a high-frequency spark. The arc heats the gas and ionizes it, producing a plasma arc. The gas expands thermally and is ejected as a high-speed plasma jet from the nozzle. The powder is delivered into the plasma jet either from the inside (internal powder feed) or outside (external powder feed), where it is heated to a molten or semi-molten state and accelerated by the plasma jet before being sprayed onto the pre-treated substrate surface to form a coating.

Coating and Process Technology Characteristics:

Coating Structure Characteristics: Plasma spraying results in dense coatings with low oxide content and porosity. For example, the porosity of chromium oxide coatings can be controlled to below 2%. The bonding between the coating and the substrate, as well as the bonding between coating particles, is primarily mechanical, but also includes metallurgical and physical bonds, giving the coating a high bonding strength.
  
Process Technology Characteristics:

Compared to other spraying methods, plasma spraying has the following characteristics
1. A wide range of sprayable materials, from low-melting-point metal alloys to high-melting-point ceramic materials.
2. High coating bonding strength, low porosity, and fewer oxide inclusions.
3. High equipment control precision, enabling the preparation of fine coatings.