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The surface composition and microstructure evolution of a second-generation Ni-based single crystal superalloy were investigated during vacuum solution heat treatment. The effects of adding argon partial pressure and not adding argon partial pressure on the surface layer of casting were studied. Results show that during the high-temperature vacuum heat treatment of the test bars, when argon partial pressure is applied during solution heat treatment, a Cr-depleted layer forms on the surface, exhibiting three-layer structure: transition layer (adjacent to the substrate) composed of γ' phase and topologically close-packed (TCP) phase; sub-surface layer composed of γ' phase, TCP phase, and β phase; surface layer composed of γ' phase and β phases. In this case, Al and Ni are deposited on the surface. Conversely, when heat treatment is conducted without argon partial pressure, a Cr-depleted layer still forms, but with a two-layer structure: transition layer composed of γ' phase and TCP phase and surface layer composed of γ' phase, TCP phase, and β phase. During vacuum heat treatment, reactions such as volatilization, deposition, oxidation, and diffusion of surface elements occur simultaneously. Depending on the temperature, vacuum level, and argon partial pressure, condensation layer, depletion layer, and interdiffusion layer may be formed on the surface. This study analyzed these phenomena in detail based on the thermodynamics and kinetics of relevant reactions.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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