粉末高温合金夹杂物引起疲劳裂纹萌生微观机理研究现状

Research Status of Micro⁃mechanism of Fatigue Crack Initiation Caused by Inclusions in Powder Superalloy

随着航空发动机的发展,对核心耐热部件涡轮盘的服役要求不断提高,镍基粉末高温合金已经成为涡轮盘的首选材料。目前在制备粉末高温合金涡轮盘时不可避免地会引入夹杂物缺陷,夹杂物的存在会导致合金的力学性能,尤其是低周疲劳性能明显降低。为建立带缺陷的粉末高温合金疲劳寿命模型,研究合金中夹杂物的开裂和萌生机理就显得十分必要。国内外学者对合金中夹杂物的成分、形状、位置、尺寸及自身特性等对疲劳性能的影响做了大量研究,并取得了一定的进展,在细观力学的尺度上解释了各种夹杂物的疲劳开裂模式机理;近年来一些学者采用先进的检测手段,从位错、残余应力和应变能等微观力学角度,对夹杂物的开裂机理进行解释。本文首先明确了粉末高温合金中夹杂物的分类、来源等问题,之后介绍了粉末高温合金疲劳寿命预测的研究方法和模型,结合目前存在的问题,指出夹杂物开裂机理研究是建立可靠粉末高温合金疲劳寿命预测模型的关键。同时思考了夹杂物导致裂纹萌生的研究目前所存在的问题,指出在研究裂纹萌生机理时,应将多尺度上的表征和特性进行联系,在微观-细观-宏观三种尺度上分析裂纹萌生过程中相互的响应关系,从而为建立考虑缺陷的粉末高温合金疲劳裂纹萌生寿命方法奠定基础。

With the development of aero⁃engine,the service requirements of turbine disk,the core heat⁃resistant component,are increasing,and nickel⁃based powder superalloy has become thefirst choice material for turbine disk.At present,it is inevitable to introduce inclusion defects in the preparation of powder superalloy turbine disk,and the existence of inclusions will lead to the obvious reduction of the mechanical properties of the alloy,especially the low cycle fatigue performance.In order to establish the fatigue life model of powder superalloy with defects,it is neces⁃sary to study the cracking and initiation mechanism of inclusions in the alloy.After clarifying the classification and source of inclusions in powder superalloys,scholars at home and abroad have done a lot of research on the influence of composition,shape,position,size and self⁃characteristics of inclusions on fatigue properties,and made some progress,explaining the fatigue cracking mode mechanism of various inclusions on the scale of micromechanics.In recent years,some scholars have used advanced detection methods to explain the cracking mechanism of inclusions from themicromechanical angles of dislocation,residual stress and strain energy.Then,the research method and model of fatigue life prediction of powder superalloy are introduced.Combined with the existing problems,it is pointed out that the study of inclusion cracking mechanism is the key to establishing a reliable fatigue life prediction model of powder superalloy.The existing problems in the research of crack initiation caused by inclusions are considered,and it is pointed out that when studying the crack initiation mechanism,the multi⁃scale characterization and characteristics should be linked,and the mutual response relationship in the crack initiation process should be analyzed on the micro⁃meso⁃macro scale,thus laying a foundation for establishing the fatigue crack initiation life method of powder superalloy considering defects.