Effect of Long-Term Thermal Exposures on Tensile Behaviors of K416B Nickel-Based Superalloy
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Effect of Long‑Term Thermal Exposures on Tensile Behaviors of K416B Nickel‑Based Superalloy Mao‑Kai Chen1,2 · Jun Xie1 · De‑Long Shu1 · Gui‑Chen Hou1 · Shu‑Ling Xun1 · Jin‑Jiang Yu1 · Li‑Rong Liu2 · Xiao‑Feng Sun1 · Yi‑Zhou Zhou1 Received: 30 October 2019 / Revised: 4 March 2020 © The Chinese Society for Metals (CSM) and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The effect of long-term thermal exposure on the tensile behavior of a high W content nickel-based superalloy K416B was investigated. The microstructure and the deformation characteristics were observed by scanning electron microscopy and transmission electron microscopy, and the phase transformation of the alloy during long-term thermal exposure was analyzed by X-ray diffraction patterns and differential thermal analysis. Results showed that after thermal exposure at 1000 °C, the MC carbides in the K416B alloy decomposed into M6C. During tensile deformation, dislocations slipping in γ matrix crossed over the M6C by Orowan bowing mechanism. With the increase of thermal exposure time, the secondary M6C reduced greatly the yield strength of the alloy at room temperature. Meanwhile, the continuous distribution of the secondary M6C with great brittleness in the grain boundary could become the main source of crack, which might change the fracture characteristic of the alloy from trans-granular to intergranular. Keywords K416B superalloy · Thermal exposure · Deformation mechanism · Fracture characteristics
1 Introduction Nickel-based superalloy with high tungsten (W) content has excellent oxidation resistance and mechanical properties [1–5]. Tungsten has prominent solid solution strengthening effect on nickel-based superalloys and the price of tungsten is much lower than other precious metals, such as Re and Ru. Therefore, nickel-based superalloy with high W content has gradually received the attention of material scientist. Yang et al. [6] studied the precipitation behavior of γ′ phase in K465 superalloy during thermal exposure, and reported that the decrease of γ/γ′ lattice mismatch induced the degeneration of the cubic degree of γ′ phase [7]. In addition, the formation of M6C carbides in the nickel-based superalloy with high tungsten content might affect the Available online at http://link.springer.com/journal/40195. * Jun Xie [email protected] 1
Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Shenyang University of Technology, Shenyang 110870, China
2
mechanical properties of the alloy [8, 9]. The research results of Xie et al. [10] and Qin et al. [11] showed that the secondary carbides precipitated with granular shape was caused by the decomposition of MC carbides at the grain boundary and followed the reactions as MC + γ → γ′ + M6C (M23C6), which could hinder the sliding of grain boundary and improved the performance of the alloy at high temperature. The tensile fracture mechanism of cast nickel-based superalloys included mainly trans-granular, intergranular and microvoid coalescence f
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