Influence of Re on High-Temperature Microstructural Stability and Mechanical Properties of High-Cr CoNi-Based Superalloys

A multicomponent high-Cr CoNi-based superalloySuperalloys was developed for potential use in industrial gas turbine materials. In response to the enhanced overall performance of alloys, the microstructural stabilityMicrostructural stability and strength of alloys with different Re additionsRe addition at 950 °C were investigated. During long-term thermal exposure, the γ′ precipitatesPrecipitates remained nearly cuboidal and the addition of Re led to a mild decrease in the γ′ volume fraction. The Re additionRe addition can effectively reduce the coarseningCoarsening rate of γ′ precipitatesPrecipitates due to both the significant reduction in the effective diffusionDiffusion coefficient in the γ matrix and the decrease in interfacial energy between the γ and γ′ phases. Despite a reduction in γ′ volume fraction, the addition of Re improved the creep propertiesCreep properties of the investigated alloys at 950 °C/200 MPa-300 MPa. Firstly, the introduction of Re causes the inversion of W partitioning from γ matrix to γ′ precipitatesPrecipitates to improve the γ′ strength. And it also elevates the content of Re within the γ phase, thereby enhancing the solid solution strengthening effect. Moreover, this improvement is also attributed to a decrease in the effective diffusionDiffusion coefficient of the alloy. All these factors contribute to improving the creep propertiesCreep properties and yield strength of high-Cr CoNi-based superalloysSuperalloys.