Plasma SprayingTechnology has been widely applied in traditional fields such as wear-resistant coatings and corrosion-resistant coatings. Since the 1950s, its applications have expanded from aerospace to steel industry, automotive manufacturing, petrochemicals, textile machinery, and shipbuilding. In recent years, the application of plasma spraying technology in fields such as nanocoatings, gradient functional materials, superconducting coatings, and biofunctional coatings has gained increasing attention.
1. Nanocoating Material
Under loads of 40-60N, the wear rate of the nano-coating is only 1/6 of that of the conventional coating. "Nano" indicates that the coating has a bimodal microstructure, demonstrating unique superior performance. The resistance to indentation cracking, bending, and cupping tests shows significantly higher adhesion resistance. The TiO2 nano-particles transition from amorphous to rutile and anatase structures. The coating exhibits good injection current and electrochemical stability. Chen Huang and others prepared zirconia nano-coatings on stainless steel substrates using atmospheric plasma spraying technology. The coating structure is dense, with a porosity of about 7%, and the adhesion strength between the coating and the substrate is 45MPa, which is notably superior to the adhesion strength of traditional zirconia coatings with substrates.
2. Gradient Functional Materials
Plasma spraying for the preparation of gradient functional materials is one of the most highly regarded research fields in materials science, primarily focusing on the design, preparation, and performance evaluation of such materials. Due to the high temperature of the plasma jet, it is particularly suitable for spraying refractory metals, ceramics, and composite coatings, providing a broader scope for the development of functional gradient materials. Compared to traditional double-layer materials, functional gradient coatings exhibit superior properties. The obtained FGM has a bonding strength of 18 MPa, while the double-layer coating has only 9 MPa. Additionally, the thermal cycling life of the FGM coating is six times that of the double-layer coating.
3. Superconducting Coating
Plasma spraying has high arc temperatures, making it particularly suitable for applying composite oxide ceramics coatings without the need for a protective atmosphere. It can coat complexly shaped superconducting components, boasts high deposition efficiency, and is easy to use for creating thick and large-area coatings. However, plasma-sprayed YBCO coatings lack superconducting properties due to oxygen loss during the spraying process, porosity, cracks, and uneven contact between particles within the coating structure. Superconductivity can only be achieved by subjecting the coating to appropriate heat treatment in an oxygen or air atmosphere, which forms a dense, uniform, and stable crystal structure. This characteristic is of special significance for plasma spraying, as it can reach temperatures of 10^6℃/s. Simply adjusting the plasma spraying conditions and process parameters makes it easy to adapt the superconducting properties of the coating state.
4. Biofunctional Coating
Plasma spraying technology is an effective method for preparing biocoating materials. After high-temperature melting, specific powdered materials are deposited on the surface of metallic artificial bone implants, forming ceramic-coated artificial bones and joints that fully utilize the advantages of both metallic and ceramic materials. There is a considerable amount of research and reports on plasma-sprayed hydroxyapatite (HA) coatings and titanium coatings both domestically and internationally, and they have been successfully applied in clinical trials. The hydroxyapatite coating is non-toxic to the body, resistant to body fluid corrosion, and has good compatibility and affinity with biological tissues, with the ability to withstand wear during long-term movement and sufficient mechanical properties. Titanium implants have good stability, excellent tissue integration, and are biocompatible with body fluids. Titanium coatings have been successfully applied to stainless steel dental roots and bone plates. These coatings not only leverage the strength of stainless steel but also utilize the biocompatibility of the titanium coating to prevent the release of toxic elements from stainless steel.
5. Other Applications
During the plasma spray process, the cooling rate of the molten particles can reach 105~106 K/s, resulting in a microstructure of amorphous phase in the coating due to this rapid cooling. High-amorphous Fe-based amorphous alloy powders (including Si, B, Cr, Ni, etc.) prepared by atmospheric plasma spray on Fe substrates.Alloy CoatingHigh density, low porosity, low oxide content, and a bonding strength of over 27 MPa. Plasma-sprayed piezoelectric ceramic coatings are used for manufacturing piezoelectric components, particularly large-area piezoelectric sensors and actuator arrays. Additionally, atmospheric plasma spraying technology has also been researched and reported in the preparation of solid oxide fuel cells (SOFC).
Plasma spray technology is a widely used material surface coating technique, known for its rapid deposition speed and high production efficiency. It is extensively applied in aerospace, automotive, and other fields, boasting a promising market application prospect.
