Creep of Single Crystals of Nickel-Based Superalloys at Ultra-High Homologous Temperature

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 49; no. 9; pp. 3973 - 3987
• Main Authors: Epishin, Alexander, Fedelich, Bernard, Nolze, Gert, Schriever, Sina, Feldmann, Titus, Ijaz, Muhammad Farzik, Viguier, Bernard, Poquillon, Dominique, Le Bouar, Yann, Ruffini, Antoine, Finel, Alphonse
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.09.2018; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Creep rate; Creep strength; Crystal structure; Deformation resistance; Dependence; Dwell time; Homology; Hot isostatic pressing; Materials Science; Metallic Materials; Nanotechnology; Necking; Nickel; Nickel base alloys; Recrystallization; Shear deformation; Single crystals; Strain; Structural Materials; Superalloys; Surfaces and Interfaces; Thin Films; Third European Symposium on Superalloys and their Applications; Topical Collection: Superalloys and Their Applications
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-018-4729-6

The creep behavior of single crystals of the nickel-based superalloy CMSX-4 was investigated at 1288 °C, which is the temperature of the hot isostatic pressing treatment applied to this superalloy in the industry. It was found that at this super-solvus temperature, where no γ ′-strengthening occurs, the superalloy is very soft and rapidly deforms under stresses between 4 and 16 MPa. The creep resistance was found to be very anisotropic, e.g. , the creep rate of [001] crystals was about 11 times higher than that of a [111] crystal. The specimens of different orientations also showed a very different necking behavior. The reduction of the cross-sectional area ψ of [001] crystals reached nearly 100 pct, while for a [111] crystal ψ  = 62 pct. The EBSD analysis of deformed specimens showed that despite such a large local strain the [001] crystals did not recrystallize, while a less deformed [111] crystal totally recrystallized within the necking zone. The recrystallization degree was found to be correlated with deformation behavior as well as with dwell time at high temperature. From the analysis of the obtained results (creep anisotropy, stress dependence of the creep rate, traces of shear deformation, and TEM observations), it was concluded that the main strain contribution resulted from 〈 01 1 ¯ 〉{111} octahedral slip.