700℃先进超超临界机组过/再热器材料C-HRA-1合金组织稳定性研究

Investigation on microstucture stability of C-HRA-1 used for superheater/reheater in 700 ℃advanced ultra-supercritical unit

研制了可工业化规模生产的700℃先进超超临界机组过/再热器用C-HRA-1镍基合金管材。采用光学显微镜、扫描电子显微镜和透射电子显微镜等分析手段,结合热力学计算,研究了C-HRA-1合金在750℃和800℃长期时效处理过程中的组织稳定性。结果表明:C-HRA-1合金管材经固溶处理后冷轧态发生完全再结晶,没有明显析出相;经800℃/12h/AC时效硬化处理后,基体上弥散分布着细小球状的γ′相,且基体中析出少量粒状MC,晶界和孪晶界析出断链状M23C6,M23C6在800℃长期时效处理中逐渐向基体溶解;750℃和800℃长期时效处理过程中,γ′相逐渐粗化并由球形趋向立方状,与时效时间相比,时效温度对γ′相粗化的影响更为显著;750℃和800℃长期时效处理过程中没有发现有害相析出,说明C-HRA-1合金管材在750℃和800℃下具有良好的组织稳定性。

The Ni-based superalloy tube C-HRA-1is manufactured under industrial process for 700 ℃ advanced ultra-supercritical unit boiler.The microstructural evolution of C-HRA-1tube during long-term thermal exposure at 750℃and 800℃ was investigated by optical microscope,scanning electron microscope（SEM）,transmission electron microscopy（TEM）and thermal calculation.The results show that,the coldrolled tube suffered fully recrystallization after solution treatment,and no obvious precipitation was observed.After age hardening treatment at 800℃/12h/AC,γ′phase with fine spherical was dispersively distributed and small amount of MC carbide particles precipitated in the matrix.In addition,M23C6 precipitated along the grain boundaries and the twinning boundaries.During long-term thermal exposure at 750 ℃and 800 ℃,theγ′phase size increased and its spherical morphology turned to cubical with increasing exposure time and exposure temperature.However,noηphase and other new precipitate was found during long term thermal exposure.It demonstrated that the microstucture stability of the C-HRA-1tube is excellent.