The process of ferrous materials and oxidized synthetic oxides. Titanium materials are stable in normal temperature air, but are easily oxidized when heated in air or in an oxidizing atmosphere. The degree of oxidation depends on the characteristics of the titanium material itself and the concentration of oxygen in the environment, heating time and heating temperature. At high temperatures, the titanium material oxidizes rapidly, causing the alloy to become brittle and the mechanical properties to deteriorate. From the point of view of oxidation resistance, the use temperature of titanium alloy should not exceed 500 ° C. Generally, the difference between the shrinkage ratio of the sample with and without oxide film is measured. As the index of oxidation degree, oxidation is the limit of high temperature of titanium material. One of the main reasons for use.

The Pilling-Bedworth ratio of titanium is greater than 1, and the molecular volume of the oxide film formed is larger than the volume of metal atoms consumed by the oxide film, so that the formed oxide film can cover the entire surface of the metal. At 500 ° C, the oxide film formed on the surface of the titanium material has a protective effect, which can prevent oxygen from permeating and prevent the titanium material from continuing to oxidize. The temperature continues to rise, the oxide film loses its protective effect, and intense oxidation occurs, and oxygen diffuses through the oxide film to the inside of the metal to form a distinct gassing layer. When the temperature is higher than 800 ° C, the oxide film decomposes, and oxygen atoms enter the metal lattice through the oxide film, and embrittlement occurs. The oxidation kinetics of titanium generally follows a parabolic law at low temperatures and a straight line at high temperatures.

Increasing the oxidation resistance of titanium materials can be achieved by coating and developing more antioxidant alloys. The coating can be surface-processed by coating a protective metal layer (such as aluminum, platinum, gold, etc.) or a mixture of metal and oxide (such as Al+SiO2) on the surface of the titanium material to enhance the oxidation resistance of the titanium material. performance. With platinum ion plating, Ti-6Al-2Sn-4Zr-2Mo does not oxidize at 590 ° C for a long time. When tungsten and platinum are used as the underlayer of the plating layer, the oxidation resistance temperature can be increased to 700 °C. Adjusting the alloy composition can also improve the oxidation resistance of the titanium material. The Pilin-Bedworth ratio of alloying elements should be greater than 1, and the free energy of Jiyin is lower than that of titanium, in accordance with Hauffe’s law.

The alloying elements that improve the oxidation resistance are: tantalum, aluminum, molybdenum, tungsten, tin, silicon, and the like. Adding these alloying elements to obtain good oxidation resistance of titanium alloys, such as Ti-5A1, Ti-5Al-2.5Sn, Ti-4Al-3Mo-1V, Ti-5.8Al-4Sn-3.5Zr-O.5Mo-O. 7Nb-O.35Si-0.06C and the like. The intermetallic compounds such as Ti3A1, Ti-Al and Ti-Al-Nb have higher oxidation resistance. The oxidation temperature of Ti3A1 can reach above 750 °C, TiAl can reach above 900 °C, and the antioxidant capacity of Ti-A1-Nb is higher. TiAl is higher.