激光增材镍基合金内部疲劳失效行为研究  

Investigation of the internal failure mechanism of laser-additively manufactured nickel-based superalloy

作　　者：孙传文[1] 李伟[1] 孙锐 SUN Chuanwen;LI Wei;SUN Rui(School of Mechanical Engineering,Beijing Institute of Technology,Beijing 100081,China;Refractory Materials Research Central,Northwest Institute for Non-Ferrous Metal Research,Xi’an 710016,China)

机构地区：[1]北京理工大学机械与车辆学院,北京100081 [2]西北有色金属研究院难熔金属材料研究所,西安710016

出　　处：《工程科学学报》2024年第12期2207-2216,共10页Chinese Journal of Engineering

基　　金：国家自然科学基金面上资助项目(52175128);西安交通大学金属材料强度国家重点实验室开放课题(20232501);湖北隆中实验室开放基金(2022KF-10);陕西省科技厅秦创原引用高层次创新创业人才项目(QCYRCXM-2022-173)。

摘　　要：内部失效是激光增材制造镍基高温合金在高温下的典型疲劳失效模式,目前对这种失效模式的认知尚不充分.在650℃下进行了不同应力比的轴向疲劳试验,随后采用扫描电镜、电子背散射衍射、聚焦离子束和透射电子显微镜等测试技术,研究了增材制造镍基高温合金的多尺度内部失效行为.结果表明,不论是否受缺陷影响,微裂纹主要从晶粒取向较软的大晶粒处萌生,然后沿最大剪切应力方向滑移和扩展,形成晶体学小平面,因此与晶粒特征相关的小平面开裂是一种典型的内部失效模式.对小平面裂纹附近的位错结构进行分析,在650℃时,局部塑性变形是由反相边界剪切、沉淀物旁通以及堆积层错剪切机制的共同作用所引起的.结合裂纹尖端应力强度因子的定义,提出了与小平面裂纹特征相关的裂纹成核寿命预测方法,预测结果与实验结果具有较好的一致性.Nickel-based superalloys exhibit excellent high strength and thermal fatigue resistance at 650℃,making them widely used for manufacturing elevated-temperature components such as turbine blades for aero-engines.Laser-powder bed fusion(L-PBF)is a rapidly developing metal additive manufacturing technology that is increasingly important for producing nickel-based superalloy products.The design and service life of aero-engine turbine blades typically require more than 107 load cycles.Therefore,it is crucial to investigate the very-high-cycle fatigue characteristics of L-PBF nickel-based superalloys at increased temperatures.Internal failure is a common elevated-temperature fatigue mode of L-PBF nickel-based superalloys that is currently not well understood.To address this issue,first,axial fatigue tests with stress ratios of−1 and 0.1 are conducted at 650℃.Specifically,partial typical internal failure fractures at a stress ratio of 0.1 are selected as the focus of this study.Second,scanning electron microscopy and ultra-depth field microscopy are employed to observe the 2D and 3D morphology of the fatigue fracture surfaces and analyze the crack nucleation areas and growth paths.The results show that irrespective of the presence of defects,the emergence and aggregation of numerous facets occur in the“facetted cracking area(FCA),”a typical internal failure characteristic of L-PBF nickel-based superalloys.Measurements indicate that the size of these facets leading to cracking is comparable to that of large grains and correlates with variations in grain orientation.Therefore,internal failures are categorized into two modes of cracking:“defect-assisted faceted cracking”and“non-defect-assisted faceted cracking.”Third,the FCA exhibiting typical internal failure fractures is sectioned and subjected to electron backscatter diffraction analysis to observe surface and subsurface crystallographic features related to crack nucleation and growth behavior.The analysis reveals that microcracks mainly originate from

关 键 词：增材制造 镍基高温合金 超高周疲劳 内部失效 位错结构 

分 类 号：TG146.1[一般工业技术—材料科学与工程]