Study On Microstructure And Properties Of Hastelloy C - 276 Nickel - Base Alloy

Nuclear energy has been paid great attention by many countries as a kind of clean energy, which is not dependent on natural conditions and less resource consumption. In nuclear power plant, the nuclear main pump is the only equipment of long-term high-speed operation in the high radiation environment, therefore, it’s crucial to ensure the main pump sealed and no leakage. Hastelloy C-276 alloy typifies anti-corrosion and high temperature resistance as well as strong resistant ability in oxidizing medium or reducing medium, the shielding sleeve made of this alloy is the key components of the main nuclear shielding pump motor. However, the shielding sleeve is very difficult to manufacture, the precipitation of second phase have a serious impact on the organization and performance in the process of production and application. In this thesis, the problems that may be encountered in the localization of C-276 and the process of hot rolled coil cooling of the actual production have been researched.In this thesis, based on the microstructure and fracture observation, in combination with physical and chemical phase analysis, EDS analysis and TEM determination, Pro-cast software for finite element simulation analysis methods.et. al, the effect of different solid solution treatment and aging treatment on the microstructure and mechanical properties of C-276 alloy were studied, as well as simulated temperature field and organizational performance during the process of hot rolled coil cooling. The following major conclusions were obtained.1. With the increase of solid solution temperature and holding time, the grain size and the work-hardening exponent n value were increased, while the yield strength was decreased, the uniform deformation ability of the alloy during plastic deformation was enhanced. It’s recommended to select the solution temperature in the range of 1150℃-1200℃ in the actual production.2. After aging treatment, the second phase of C-276 alloy precipitated in the grain boundary till saturation, then precipitated in the grain. And the second phase included mainly Mo-rich M6C and μ phase. The impact performance of C-276 alloy was significant reduced with the increase of holding time. C-276 alloy was sensitive to precipitation around 980℃.3. C-276 alloy rolled coil can be dropped to below 650℃ after 5-5.5 h, namely droped to the extent of precipitation sensitive temperature. The microstructure evolution in the process of cooling was not a serious impact on its room-temperature mechanical properties, the room-temperature ductility and toughness were still high.