Effect of Zr addition on the microstructure and intermediate-temperature mechanical performance of a Ni–26W–6Cr based superalloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2022-01, Vol.833, p.142517, Article 142517
• Main Authors: Liu, Shulin, Ye, Xiang-Xi, Jiang, Li, Liu, Renduo, Gao, Zhenhuan, Gong, Xiufang, Li, Zhijun, Zhou, Xingtai
• Format: Article
• Language: English
• Subjects: Carbides; Constitutional undercooling; Dynamic recrystallization; Elongation; Gamma phase; Grain boundaries; Grain growth; Grain size; Hot rolling; Interfacial energy; Intermediate temperature ductility; Liquid-solid interfaces; Mechanical properties; Ni-26W–6Cr; Nickel base alloys; Nucleation; Solidification; Solution heat treatment; Superalloys; Supercooling; Ultimate tensile strength; Zirconium
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2021.142517

In the present work, Zr was added into a Ni–26W–6Cr alloy to improve the intermediate temperature ductility, and the corresponding mechanism was discussed. The enrichment of Zr at the solid-liquid interface during the solidification process causes constitutional undercooling and a decrease of interfacial energy, which can promote the nucleation of the γ phase. The average γ grain size after hot rolling and solution treatment is reduced from 41.7 μm to 20.0 μm with the addition of Zr from 0 to 0.081 wt%. The Zr-bearing Ni–26W–6Cr alloys with finer as-cast initial grains tend to develop into smaller recrystallized grains after thermal deformation and solution treatment. Besides, the enrichment of Zr and C at the solid-liquid interface increases the number of M6C carbides in the alloys, impeding the grain growth of γ. The refined grains and the increased M6C carbides effectively hinder the movement of dislocation during tensile. The yield strength and ultimate tensile strength at 650 °C are improved from 227 MPa to 274 MPa, 431 MPa to 492 MPa, respectively. The improvement of elongation is attributed to the larger fraction of dynamic recrystallization that releases the local stress caused by dislocation accumulation at the grain boundaries. [Display omitted] •Zr can improve the tensile strength and ductility of Ni–26W–6Cr alloy at 650 °C.•Zr increases the nucleation rate of γ matrix and the number of M6C carbides.•Dynamic recrystallization contributes to the improvement of elongation at 650 °C.