GH4033合金短時超溫后的顯微組織損傷及力學(xué)性能MICROSTRUCTURAL DEGRADATION AND MECHANICAL PROPERTIES OF GH4033 ALLOY AFTER OVERHEATING FOR SHORT TIME

對已服役的航空發(fā)動機用GH4033合金二級渦輪葉片榫頭部位進行900~1100 ℃短時超溫3 min熱處理, 之后再進行組織表征和力學(xué)性能測試, 研究了合金短時超溫過程中的組織損傷及其對室溫硬度和700 ℃, 430 MPa 下持久壽命的影響規(guī)律. 結(jié)果表明, GH4033合金中γ′相顆粒在短時超溫過程中發(fā)生粗化和回溶現(xiàn)象, 當(dāng)溫度達到980 ℃及以上時, 保溫 3 min后γ′相完全回溶; 隨著超溫溫度的升高, 晶界碳化物逐漸溶解, 1100 ℃時完全溶解, 并造成晶粒開始長大. 短時超溫后葉片合金的室溫硬度隨著γ′相的回溶急劇下降, 當(dāng)γ′相完全回溶時室溫硬度降低至 170 HV 左右. 合金在700 ℃, 430 MPa 下持久壽命隨著短時超溫溫度的升高呈現(xiàn)先增大后急劇降低的規(guī)律, 其主要受γ′相的回溶與再析出以及晶界碳化物回溶的影響.

Service safety of turbine blades in aircraft engines are threatened by microstructural and property degradation instantly caused by overheating during service. Systematic investigations about microstructural degradation during overheating exposures and its influence on mechanical properties of turbine blades during service are limitedly reported. In this work, microstructure and mechanical properties of GH4033 alloy, which was sectioned from the shank of a serviced 2nd stage turbine blade in an aircraft engine, were studied after overheating at 900~1100 ℃ for 3 min. Microstructural degradation during overheating exposures as well as its influence on room temperature hardness and stress rupture life at 700 ℃, 430 MPa were analyzed. The results of microstructural characterization indicated that the coarsening and dissolution of γ′ precipitates were introduced by overheating exposures, and all of the γ′ precipitates dissolved at 980 ℃ for 3 min. Gradual dissolution of grain boundary (GB) carbides was observed with the increase of overheating temperature. Complete dissolution of GB carbides at 1100 ℃ resulted in grain growth. The room temperature hardness after overheating exposures decreased grossly with the dissolution of γ′ phase. Due to the dissolution and re-precipitation of γ′ phase as well as the dissolution of GB carbides, the stress rupture life under 700 ℃, 430 MPa of GH4033 alloy was initially increased and then decreased significantly.

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