镍基单晶高温合金冷热循环过程中圆孔周围裂纹萌生与扩展行为
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- 英文论文题名：Crack Initiation and Propagation around Holes of Ni-based Single Crystal Superalloy during Thermal Fatigue Cycle
- 论文作者：王莉 ; 周忠娇 ; 张少华 ; 降向冬 ; 楼琅洪 ; 张健
- 英文论文作者：Wang Li ; Zhou Zhongjiao ; Zhang Shaohua ; Jiang Xiangdong ; Lou Langhong ; Zhang Jian ; Institute of Metal Research ; Chinese Academy of Sciences ; Beijing Beiye Functional Materials Corporation
- 年：2015
- 作者机构：中国科学院金属研究所高温合金部;北京北冶功能材料有限公司;
- 论文关键词：镍基单晶高温合金 ; 晶体学取向 ; 热疲劳 ; 孔 ; 裂纹萌生及扩展
- 英文论文关键词：Ni-based single crystal superalloy ; crystal orientation ; thermal fatigue ; hole ; crack initiation and propagation
- 会议召开时间：2015-05-20
- 会议录名称：第十三届中国高温合金年会论文集
- 英文会议录名称：Proceedings of the 13th China Superalloys Conference
- 语种：中文
- 分类号：TG132.3
- 学会代码：ZGJS
- 会议名称：第十三届中国高温合金年会
- 会议地点：中国北京
- 主办单位：中国金属学会高温材料分会
- 学会名称：中国金属学会
- 页数：1
- 文件大小：69k
- 原文格式：O
- 会议级别：全国
摘要
选用第二代镍基单晶高温合金,制备了平行于定向凝固方向且分别沿(100)面和(110)面的2组板式试样,采用电火花方法在试样中心垂直于板面加工孔径为0.5mm的圆孔。采用室温到1100℃的冷热疲劳实验,研究了冷热循环过程中不同晶体学平面的板式试样上圆孔周围裂纹萌生及扩展行为。结果表明,位于不同晶体学平面的板式试样中,电火花方法加工圆孔周围产生了一薄层再铸层,再铸层最厚处约15μm。板式试样所在晶体学平面对圆孔周围裂纹萌生及扩展行为影响显著。冷热循环80cyc后,(1 10)面试样中,裂纹在与枝晶生长方向垂直的孔边产生,之后迅速沿与枝晶生长呈45°角方向扩展。而对于(100)面试样,即使经过200cyc冷热循环后孔边也未观察到裂纹,造成此差异的本质原因是单晶高温合金晶体结构的各向异性导致的热应力差别与微观组织特征共同作用的结果。
Ni-based single crystal(SX) superalloys are widely used for production of blades in gas turbines and aircraft engines for their superior mechanical performance at high temperatures.To obtain high cooling efficiency,most of the SX blades consist of thin wall with cooling holes.However,thermal fatigue cracks are usually observed in blades with this kind of structures.Thus,it must be valuable to investigate the crack initiation and propagation around a hole during thermal fatigue tests in a SX superalloy.In the present work a second generation SX Ni-based superalloy was used.Plate specimens that parallel to directional solidification(DS) direction and along(100) or(110) planes were prepared.A hole with diameter of 0.5 mm was drilled vertical to the surface in the middle of the plate by electro-discharge machining(EDM).Thermal fatigue tests were performed between room temperature and 1000℃.Effect of crystal orientation on the crack initiation and propagation was investigated and the reasons were analyzed.It was found that a thin recast layer was produced around holes of EDM drilled.The thickness of the recast layer was 15μm in the maximum.Crystal orientation has great effect on the crack initiation sites and propagation kinetics.After 80 cyc thermal fatigue tests,in(110) specimens cracks initiated at the edge of the holes that vertical to the DS direction,then grew quickly and propagated along directions about 45° from the DS direction.After 200 cyc tests,cracks developed to more than 2 mm in length.While in(100) specimens no cracks could be observed even after 200 cyc thermal fatigue tests.This difference was mainly due to the combined effects of different thermal stress caused by the anisotropy of single crystals and of the microstructure characteristics.
Ni-based single crystal(SX) superalloys are widely used for production of blades in gas turbines and aircraft engines for their superior mechanical performance at high temperatures.To obtain high cooling efficiency,most of the SX blades consist of thin wall with cooling holes.However,thermal fatigue cracks are usually observed in blades with this kind of structures.Thus,it must be valuable to investigate the crack initiation and propagation around a hole during thermal fatigue tests in a SX superalloy.In the present work a second generation SX Ni-based superalloy was used.Plate specimens that parallel to directional solidification(DS) direction and along(100) or(110) planes were prepared.A hole with diameter of 0.5 mm was drilled vertical to the surface in the middle of the plate by electro-discharge machining(EDM).Thermal fatigue tests were performed between room temperature and 1000℃.Effect of crystal orientation on the crack initiation and propagation was investigated and the reasons were analyzed.It was found that a thin recast layer was produced around holes of EDM drilled.The thickness of the recast layer was 15μm in the maximum.Crystal orientation has great effect on the crack initiation sites and propagation kinetics.After 80 cyc thermal fatigue tests,in(110) specimens cracks initiated at the edge of the holes that vertical to the DS direction,then grew quickly and propagated along directions about 45° from the DS direction.After 200 cyc tests,cracks developed to more than 2 mm in length.While in(100) specimens no cracks could be observed even after 200 cyc thermal fatigue tests.This difference was mainly due to the combined effects of different thermal stress caused by the anisotropy of single crystals and of the microstructure characteristics.
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