Inconel 718合金涡轮盘服役后一次碳化物演变规律及微区力学性能的研究

Research on the Evolution Behavior and Micro-Zone Mechanical Properties of the Primary Carbides in Inconel 718 Superalloy Service Turbine Disk

摘要:

以某型号客机累积服役时间约60 000 h的Inconel 718（GH4169）涡轮盘为研究对象，系统研究了长时间服役后涡轮盘内不同位置下微观组织的演变情况。利用光学显微镜、扫描电镜、电子探针、萃取相分析、夹杂物扫描仪和纳米压痕等方法对其组织演变行为进行了详细表征。结果表明，在长期服役后，涡轮盘内主要强化相γ'和γ'未发生显著变化。但是，基体内弥散分布的一次MC碳化物沉淀相，自涡轮盘心部至边缘位置其数量、大小和形貌均明显变化。合金内部一次MC碳化物含量由0.166wt%降低至0.106wt%，其形貌由规整的块状逐渐向不规则的近圆形状转变。同时涡轮盘内发生元素重新分布行为，碳化物的回溶使Nb、Ti、C元素扩散进入基体，导致碳化物的纳米硬度降低而碳化物附近基体内纳米硬度略微上升。因此，在Inconel 718合金涡轮盘实际服役过程中，不同于传统认知中的一次碳化物具有极高的稳定性这一观点，合金内一次MC碳化物会发生缓慢的回溶现象。而碳化物的失稳以及回溶后部分碳化物形成元素扩散进入基体中的行为，会对合金长期服役的综合力学性能产生“扰动”。

Abstract:

Taking an Inconel 718 (GH4169) turbine disk with an accumulated service time of approximately 60 000 h from a specific model of aircraft as the research object, the microstructure evolution of various regions of the service turbine disk was investigated. Detailed characterization of the microstructure was conducted using research methods such as optical microscopy, scanning electron microscopy, electron probe, extraction phase analysis, inclusion scanner, and nano-indentation. The results show that after long-term service, there is no significant change in the strengthening phases γ' and γ' of the turbine disk. However, the quantity, size, and morphology of primary MC carbides from the center to the edge have noticeable changes. The content decreases from 0.166wt% to 0.106wt%, and the morphology gradually changes from sharp and regular blocky at the interface to irregular near-circular ones. The nano-hardness decreases, and there is a significant redistribution of elements, with elements Nb, Ti, and C released and diffused into the matrix. The primary MC carbides are prone to dissolution and decomposition during long-term service, leading to a decrease in concentration and hardness of the carbide elements. The diffusion of carbide-forming elements into the matrix may cause a disturbance to the comprehensive mechanical properties of the alloy during the long-term service performance.