预热处理对一种新型镍基粉末高温合金涡轮盘锻态显微组织的影响

Miscrostructure study of preheating treatment on a Novel Nickel-Based Superalloy turbine disc

摘要:

本工作研究了复合亚固溶热处理工艺对一种新型镍基粉末高温合金FGH4113A(WZ-A3)γ"相组织的影响规律。大尺寸锻造态涡轮盘件锻后冷速较低，γ"相的尺寸在约100nm至4500nm之间分布。在盘件上取小试样进行热处理实验，试样升温至1000℃和1050℃时，γ"相总占比下降，Oswald熟化机制及PAM机制同时存在。试样升温至1100℃时，晶内γ"相完全回溶。使用复合亚固溶热处理工艺，先将试样升温至1120℃度保温2h，快速冷却后再分别升温至1000℃、1050℃和1100℃时，γ"相总占比均下降，晶内γ"相演变以Oswald熟化机制为主导，其形貌及尺寸在升温过程中相对稳定。在盘件上取性能试棒分别进行锻造态+1000℃（不保温）+时效热处理和锻造态+1120℃（2h），80℃/min+1000℃空冷+时效热处理后进行550℃拉伸测试，后者的屈服强度和抗拉强度显著高于前者，可为大尺寸涡轮盘件的双性能热处理工艺的制定提供参考。

Abstract:

The effect of two-step sub-solvus heat treatment process on the γ "phase microstructure of a novel nickel-based powder metallurgy superalloy FGH4113A (WZ-A3) was studied. The cooling rate of large-size forged turbine disc is lower after forging, and the size distribution of γ" phases is from about 100nm to 4500nm. Small samples were taken from the disc for heat treatment experiments. When the samples were heated to 1000 ℃ and 1050 ℃, the total proportion of γ "phases decreased, and the evolution mechanism showed signs of Oswald coarsening mechanism and PAM mechanism. When the sample was heated to 1100 ℃, the intracrystalline γ" phase was completely dissolved. If two-step sub-solid solution heat treatment process was used, the sample was first heated to 1120 ℃ for 2h followed by rapid cooling, and then heated to 1000 ℃, 1050 ℃ or 1100 ℃, the total proportion of γ "phases decreased. The evolution of intracrystalline γ" phases was dominated by the Oswald coarsening mechanism, and its morphology and size were relatively stable during the heating process. The testing rods were cut from the disc and went through as forged state + 1000 ℃ (without heat preservation) + aging heat treatment and as forged state + 1120 ℃ (2h) + aging heat treatment respectively, and followed by tensile test at 550 ℃. The yield and tensile strengths of the latter one are significantly higher than the first one, and this can be treated as a reference for dual-performance heat treatment process design of large-size turbine discs.