1. Homogenization effects by Co additions to high temperature and low stress creep performance of a 4th-generation Ni-based single crystal superalloys.
- Author
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Pan, Qinghai, Zhao, Xinbao, Xia, Wanshun, Cheng, Yuan, Zhou, Yu, Fan, Yunpeng, Yue, Quanzhao, Gu, Yuefeng, and Zhang, Ze
- Subjects
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STRAINS & stresses (Mechanics) , *SINGLE crystals , *LOW temperatures , *HIGH temperatures , *HEAT resistant alloys , *NICKEL alloys - Abstract
The important factors limiting the fourth-generation Ni-based single-crystal superalloys (Ni-SXs) are the increases in cost and density. A cheaper and lighter potential alternative element of Ru, Co's comprehensive effects were studied. The effects of Co and inhomogeneity between dendrite core (DC) and interdendritic region (ID) on creep performance at 1100 °C and 137 MPa in a 4th generation Ni-SXs were systematically investigated. The results show that the Ni-SXs with 9 wt% Co has the longest creep lifetime. Co additions alleviate the overall element segregations between DC and ID, especially Re, Cr, and W. And reverse partitioning behavior of Co also changes the partitioning ratio of elements between γ and γ′ phases, resulting in the inhibition of TCP phases precipitation for most creep time to avoid excessive consumption of solid solution strengthening elements and local stress concentration. The decrease of the lattice constant of γ reduces lattice misfit between γ and γ′ with the addition of Co, leading to the enlargement of dislocation network spacing and less resistance for movement or shearing of dislocation. The decrease of γ′ solvus temperature with Co addition promotes the dissolution of γ′ at high working temperature, resulting in severe topological inversion of γ/γ′ microstructures at ID. In addition, the main creep cracks of all Ni-SXs appear at ID, so the inhomogeneity between DC and ID is concerned. • The precipitation of TCP phases are inhibited with Co addition, which is a basis of low-cost and low-density alloy design. • The comprehensive effects of Co on high temperature creep properties are investigated and an optimal Co content exists. • The increase of Co affected the γ′ phase content, lattice mismatch, element distribution and TCP phase. • The effect of Co on microstructures evolution varies at different creep stages. • The inhomogeneity between dendrite core and interdendritic region causes creep cracks originate from interdendritic region. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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