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Study of Metallic Carbide (MC) in a Ni-Co-Cr-Based Powder Metallurgy Superalloy |
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| Authors: | Wen-Bin Ma Guo-Quan Liu Ben-Fu Hu Peng-Hui Hu Yi-Wen Zhang |
| Affiliation: | 1. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P.R China 2. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing, P.R. China 3. High Temperature Materials Research Institute, Central Iron and Steel Research Institute, Beijing, 100081, P.R. China |
| Abstract: | The evolution of carbides in a Ni-Cr-Co-based powder metallurgy (PM) superalloy in the as-atomized, as-atomized + annealed, hot isostatic pressed (HIPed) and HIPed + annealed conditions were systematically analyzed to understand the formation of blocky metallic carbide (MC) along the previous particle boundary (PPB). The results show that the carbides both on the powder surfaces and in the bulk of the powder particles are mainly fan-shaped MC whose decomposition temperatures are in the range of 1473 K to 1493 K (1200 °C to 1220 °C). PPB carbides in the HIPed alloy are mainly block-shaped MC, and the fan-shaped MC densely distributed in the area that have not been consumed by the recrystallized grains. The formation mechanism of PPB carbides can be described as follows: When the powders are HIPed at 1453 K (1180 °C), the fan-shaped carbides are decomposed at the migrating boundaries of recrystallized grains, and the preferential precipitation of block-shaped MC at PPB is promoted by the carbide-forming elements released by the fan-shaped carbides. When the HIPed alloy is annealed at 1453 K (1180 °C), the area fraction of PPB carbides increases with an increase in annealing time but that of the fan-shaped carbides exhibits opposite behavior. This proves the above formation mechanism of PPB carbides. |
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