复合亚固溶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

Effects of Two-Step Sub-solution Heat Treatment on Microstructure of New As-Forged Nickel-Based Powder Superalloy Turbine Disc

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。结果表明,大尺寸锻造态涡轮盘件锻后冷速较低,γ’相的尺寸在100~4500 nm之间分布。在盘件上取小试样进行热处理试验,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℃保温2 h,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℃+815℃/8h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。

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