相图计算辅助新型Co基变形高温合金的成分设计

Composition Optimization Design for Novel Co-based Deformed Superalloy Aided by Phase Diagram Calculation Approach

摘要:

为了确定Co-Al-W-Ni-Ta-Ti体系新型γ′强化的Co-Al-W基变形高温合金的成分及相应的热处理工艺,利用Pandat计算软件及钴基高温合金热力学数据库,计算了合金元素对平衡相析出行为的影响,计算表明：W、Ni、Ta及Ti均能提高γˊ的稳定性,W、Ta会增加有害相χ-D0₁₉的析出倾向,Ti和Ni能分别抑制有害相χ-D0₁₉和B2相的析出,将合金成分定为Co-9Al-3W-30Ni-2Ta-3.5Ti(at%)。计算了此合金的相转变规律,结果表明：合金的平衡析出相为γ、γˊ、χ-D0₁₉和Co₇Ta₂,开始析出温度分别为1355℃,1169℃,700℃和288℃。制定了合金的热处理制度：1250℃/12h均匀化,1150℃/6h固溶处理,900℃/4h+750℃/16h两步时效处理。采用真空感应熔炼制备了合金样品,经上述热处理后,DSC分析结果与计算的相转变规律一致,SEM及XRD结果表明,合金中的平衡相为典型的γ+γˊ两相组织。

Abstract:

In order to determine the composition of the novel γ′ strengthened Co-Al-W-based wrought superalloy of the Co-Al-W-Ni-Ta-Ti system and the corresponding heat treatment process, using Pandat calculation software and the thermodynamic database of cobalt-based superalloys, The influence of alloying elements on the precipitation behavior of the equilibrium phase was calculated. The calculations showed that: W, Ni, Ta, and Ti can improve the stability of γˊ, W, Ta can increase the precipitation tendency of the harmful phase χ-D0₁₉, and Ti and Ni can be suppressed the precipitation of the harmful phases χ-D0₁₉ and B2 phase respectively, the alloy composition was determined as Co-9Al-3W-30Ni-2Ta-3.5Ti (at%). The phase transition law of this alloy was calculated, and the results showed that the equilibrium precipitation phases of the alloy were γ, γˊ, χ-D0₁₉ and Co₇Ta₂, and the initial precipitation temperatures were 1355 °C, 1169 ° C, 700 ° C, and 288 ° C, respectively. The alloy heat treatment process was formulated: 1250℃/12h homogenization, 1150℃/6h solution treatment, 900℃/4h + 750℃/16h two-step aging treatment. The alloy samples were prepared by vacuum induction melting. After the above heat treatment, the DSC analysis results are consistent with the calculated phase transition rules. SEM and XRD results show that the equilibrium phase of the alloy is typical γ + γˊ two-phase structure.