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<p>This study investigates the effect of overtemperature treatment (OTT) on microstructure and high-cycle fatigue property of DD32 single crystal Ni-base superalloy. The DD32 alloy, following standard heat treatment, was subjected to OTT at 1150, 1180, and 1200&#xa0;°C, then observed the changes in microstructure. The results indicate that OTT can lead to the degree of cubic and homogenization of γ′ phase decreasing, while the width of the matrix channel increases, and small secondary γ′ precipitates occur in the matrix channel. The degradation and dissolution of γ′ phase become more pronounced with the prolongation of overtemperature time and temperature rise, resulting in the formation of numerous fine secondary γ′ particles. After OTT, the DD32 alloy contains a certain quantity of carbides and TCP phases. The quantity of TCP phases will increase after long-term OTT, whereas carbides tend to decompose. The high-cycle fatigue property of the DD32 alloy does not change much after 100 hours OTT at both 1150 and 1200&#xa0;°C. After more than 100 hours OTT at 1200&#xa0;°C, as most of the γ′ phases dissolve, the fatigue life of the alloy begins to decrease. After fatigue testing at 900&#xa0;°C, dislocation bypass γ′ phase is the primary mode of motion in samples after standard heat treatment. In contrast, dislocation networks deposit at the γ/γ′ phase interface in samples subjected to various OTT conditions.</p>

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The Effect of Overtemperature on the Microstructure and High-Cycle Fatigue Property of DD32 Single Crystal Alloy

  • 期刊论文

  • 发表日期：

    2025年8月29日

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  • Chang-tai Jiang,
  • Jin-lai Liu,
  • Jin-jiang Yu,
  • Yi-zhou Zhou,
  • Xiao-feng Sun

摘要

This study investigates the effect of overtemperature treatment (OTT) on microstructure and high-cycle fatigue property of DD32 single crystal Ni-base superalloy. The DD32 alloy, following standard heat treatment, was subjected to OTT at 1150, 1180, and 1200 °C, then observed the changes in microstructure. The results indicate that OTT can lead to the degree of cubic and homogenization of γ′ phase decreasing, while the width of the matrix channel increases, and small secondary γ′ precipitates occur in the matrix channel. The degradation and dissolution of γ′ phase become more pronounced with the prolongation of overtemperature time and temperature rise, resulting in the formation of numerous fine secondary γ′ particles. After OTT, the DD32 alloy contains a certain quantity of carbides and TCP phases. The quantity of TCP phases will increase after long-term OTT, whereas carbides tend to decompose. The high-cycle fatigue property of the DD32 alloy does not change much after 100 hours OTT at both 1150 and 1200 °C. After more than 100 hours OTT at 1200 °C, as most of the γ′ phases dissolve, the fatigue life of the alloy begins to decrease. After fatigue testing at 900 °C, dislocation bypass γ′ phase is the primary mode of motion in samples after standard heat treatment. In contrast, dislocation networks deposit at the γ/γ′ phase interface in samples subjected to various OTT conditions.