摘要
The fatigue test between 10^5—10^9 cycles of GH4169 nickel‑based superalloy commonly used in aircraft engines is carried out by ultrasonic fatigue machine at 650℃.The S‑N curve is obtained and the fatigue fracture morphology is observed.The fatigue S‑N curve presents a“step‑like”shape,with the first inflection point near 1×10^7 cycles and the second inflection point near 1×10^8 cycles.There is no engineering fatigue limit,and it still shows a downward trend after 107 or even 10^9 cycles.The crack initiation location is related to its life.Cracks are generated on the surface below 10^7 cycles,while it is inside above 10^7 cycles.The crack initiation source in the ultra‑high cycle fatigue at 650℃ is mainly the local intergranular fracture and casting defect of the matrix.In the phase of crack propagation,the mixed propagation of intergranular and cleavage is the main form.
采用超声疲劳试验设备,对航空发动机常用的GH4169合金在650℃下进行了10^5~10^9周次的疲劳试验。通过对疲劳S‑N曲线及疲劳断口形貌的分析,得出以下结论∶S‑N曲线呈现“阶梯状”,第1个拐点出现在10^7周次附近,第2个拐点出现在10^8周次附近。曲线不存在疲劳极限,经过10^7次甚至10^9次循环后仍呈现下降趋势。裂纹萌生的位置与寿命有关,在10^7周次以下裂纹均萌生于表面,10^7周次之后裂纹均萌生于内部。内部起裂源头主要为局部的沿晶断裂和铸造缺陷,裂纹扩展以沿晶和解理的混合断裂为主。
基金
supported by the Tianjin Technical Expert Project (No.19JCTPJC43800)
the Tianjin Science and Technology Planning Project (No. 19YFFCYS00090)
the Key Project of Science and Technology Cultivation of Tianjin Sino-German University of Applied Technology(No. zdkt2017-006)
the Priority Academic Program Development of Jiangsu Higher Education Institutions
