With the rapid development of modern industry and high technology, new materials with high temperature resistance, oxidation resistance and corrosion resistance have been put forward more and more urgently. For example, in order to improve the heat conversion efficiency and energy efficiency of advanced aero-engines, the gas temperature needs to be further improved. The gas temperature has approached or even exceeded the limit service temperature (1200℃) of common nickel-based superalloy. The satellite's nuclear fuel cladding material with isotopic battery needs to withstand the high temperature of about 1400℃ and work for 3-5 years or even longer, which provides power for the satellite's long-term scientific research and exploration work. The nozzle material used in supersonic wind tunnel should be exposed to 1500℃ oxidation atmosphere for long-term use. The operating temperature of the third-generation space engine combustion chamber exceeds 1800℃, and the application environment is extremely harsh. In high temperature experiments of high temperature gas measurement and intraocular lens drawing, the temperature can exceed 2000℃[1-4]. These applications require not only excellent mechanical properties at high temperature, but also excellent oxidation resistance and corrosion resistance at high temperature. Structural ceramics and refractory alloys are currently the preferred high temperature materials.
Although ceramics have enough strength at high temperature, their brittleness and strong environmental sensitivity limit their application. Refractory alloys such as niobium and tantalum alloys have high melting point and good toughness, but poor oxidation resistance at high temperature, so they cannot be used in high temperature oxidation environment directly. Therefore, suitable high performance coatings must be developed. It is particularly urgent to develop new high-temperature materials that can be directly applied under extreme conditions such as oxidation and corrosion at high temperature (above 1200℃). The precious metal iridium has a high melting point (2447℃), and has strong corrosion resistance, thermal stability and high temperature strength. It has been applied in the field of traditional high-temperature materials, such as crucible materials, stirring rods and wire. However, the high temperature oxidation resistance and room temperature plasticity of pure iridium have greatly limited its application range, and the enhancement of the high temperature oxidation resistance and room temperature plasticity of iridium has been a research hotspot and a long-term goal in the field of high-temperature materials [5]. The research and application show that adding precious metal rhodium to iridium can significantly improve the oxidation resistance and processing performance of the material. In platinum group metals, rhodium has a melting point (1963℃) second only to iridium, and both can form solid solutions in the entire composition range, so iridium rhodium alloy is an ideal material for use at ultra-high temperatures [6]. In this paper, iridium and a series of iridium rhodium alloys were selected and oxidized at 1550℃ to investigate the effect of rhodium addition on the oxidation properties of iridium alloys at high temperature.
