The high temperature oxidation resistance and thermal shock resistance of tantalum tungsten/iridium coating were studied by vacuum arc ion deposition technique. The results show that the iridium coating can effectively protect the tantalum tungsten alloy at 800℃ and 1 100℃. After 20 h, only slight oxidation occurs on the surface of the iridium coating, and brown iridium oxide products are formed on the surface. At 1 900℃, the antioxidant life was more than 10 h. Under the condition of thermal shock from room temperature to (1 900 ±50) ℃, its life can reach more than 1 000 times.
Common high-temperature oxidation resistant coatings of tantalum tungsten alloy include heat-resistant alloy coating, aluminide coating, silicide coating and precious metal coating, among which iridium has a high melting point (2 443 ℃) and excellent oxidation resistance at 2 100 ℃. Studies in literature show that iridium oxide resistant coating is used on nozzle of liquid rocket engine for orbit entry and attitude control of space vehicle. The inner wall of nozzle does not need fuel liquid film cooling, which improves the specific impulse and life of engine and increases the payload of satellite, and has great application prospects. Therefore, the preparation of iridium - resistant coating on tantalum-tungsten alloy has scientific significance and application value.
A continuous uniform and dense iridium coating was prepared on the surface of Ta-10W alloy by vacuum arc ion deposition technology, and the iridium coating was tested by constant temperature oxidation at 800, 1 100 and 1 900 ℃ and thermal shock at room temperature up to (1 900 ± 50) ℃. At the same time, the high temperature oxidation behavior and anti-oxidation failure mechanism of iridium coating were analyzed.
Test piece performance test: low voltage and high current direct current heating method, infrared thermometer for temperature measurement. According to the operating characteristics of the orbital attitude control dual-component liquid rocket engine, the steady-state operating temperature of the engine is designed to be 1 900 ℃, and the pulse operating temperature of the engine is designed to be 800 ~1 100 ℃. Therefore, in the static air, the test pieces are heated to 800, 1 10 and 1 900 ℃ respectively within 30 s for insulation. Observe and record the time of coating defects. According to the engine cold and hot start and shut down conditions, the thermal shock test is 15 s from room temperature to (1 900 ± 50) ℃, held at (1 900 ± 50) ℃ for 3 s, and then 15 s from (1 900 ± 50) ℃ cooling to room temperature, cyclic thermal shock test.
