Alumina coating structure and performance

       

Alumina coating structure and performance

Because the melting point of TiO2 is lower than that of Al2O3, and the wettability is better than that of Al2O3, TiO2 ceramic coating has very low porosity, good wear resistance, resistance to chemical reactions, good toughness, easy processing, and can be ground to a very high degree. High surface finish, resistant to most acids, salts and solvents, is an important corrosion-resistant coating, especially suitable for titanium and titanium alloys, aluminum and alloys to spray high wear-resistant coatings. It is precisely because plasma sprayed alumina coating has been widely used in the industry, but the plasma spraying process restricts the quality of the coating. Laser remelting provides a new way to solve this technical problem. Laser remelting can overcome the plasma sprayed film. Laminar, high porosity, many cracks, mechanical bonding between the coating and the substrate and other defects. Domestic and foreign scholars combine laser remelting technology and plasma spraying technology to prepare alumina ceramic composite coatings, and explore the influence of laser remelting on the structure and performance of ceramic coatings.

TiO2 has these characteristics, so that the quality of Al2O3-TiO2 coating is better than that of single laser remelting plasma sprayed Al coating. At present, intensive research is being conducted on TiO2 (abbreviated as AT13, the same below) coating, which has excellent comprehensive properties such as wear resistance, corrosion resistance and insulation below 540 ℃.

Plasma spraying is used to prepare Al2O3-TiO2 coating. The ceramic coating is mainly composed of rutile TiO2, anatase TiO2, Magneli phase and γ-Al2O3, and also contains a small amount of α-Al2O3 and microcrystalline or amorphous. Compared with the Al2O3 coating, the addition of TiO2 in the AT13 coating makes the ceramic layer more compact with reduced porosity. Compared with Al2O3 coating, the hardness of AT13 coating is lower, but the dispersion of hardness distribution is smaller, and the uniformity of the coating is better. Under the same friction and wear test conditions, AT13 coating has better wear resistance than Al2O3 coating. The thermal shock resistance of the gradient coating prepared by spraying is better than that of the non-gradient coating. The gradient of the coating composition alleviates the thermal stress and improves the thermal shock failure resistance.