What are the properties and application characteristics of alumina ceramics

       Among the oxides with melting points above 2000 degrees Celsius, alumina is the most flexible and cheapest material. It is abundant in nature and generally exists in two forms. One is called natural corundum, or a-AI2O3, colored rubies and sapphires are different variants of corundum, and the other is bauxite.

    The alumina powder used for thermal spraying is a high-purity a-AI2O3o obtained by smelting and pulverizing. The a-AI2O3 crystal form is the most stable hexagonal structure among various variants, and has good thermal cycle resistance.

    Alumina can be widely used as heat insulating coating, high temperature resistant coating, wear resistant coating and insulating coating. Bond strength and protect the workpiece substrate from oxidation or corrosion; when used as a wear-resistant coating, the power should be increased during spraying to ensure that the powder is fully melted and the coating material is reduced. For example, it can be used in blast furnace tuyere and slag port to improve its service life; it is used in rocket and jet engine nozzles to prevent the erosion of high temperature airflow; in recent years, it has been used to prevent chemical medium corrosion.

    However, the alumina coating cannot withstand impact loads and local collisions, otherwise it will cause damage and peeling of the coating. In order to improve the properties of alumina and increase the density of the coating, it is often mixed with titanium oxide or composited with nickel and aluminum, and its coating toughness and impact resistance are better than pure alumina. For example, a coating made by adding a certain amount of TiO2, Cr2O3, and SiO2 to alumina will not undergo phase change due to heating and cooling. As a result, the overall performance of the coating and workpiece substrate and thermal cycle resistance can be improved.