High-temperature fatigue strength of grain boundaries with different misorientations in nickel-based superalloy bicrystals  

作　　者：D.F.Shi Z.J.Zhang Y.H.Yang Y.Z.Zhou R.Liu P.Zhang Z.F.Zhang 

机构地区：[1]Shi-changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China [2]School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China

出　　处：《Journal of Materials Science & Technology》2023年第23期94-106,共13页材料科学技术（英文版）

摘　　要：Nickel-based single-crystal superalloys are widely used in the manufacture of aeroengine turbine vanes for their excellent high-temperature performance. Low-angle grain boundaries (LAGBs) will be generated inevitably during their manufacture, which are often characterized by grain boundary misorientation (GBM) and will weaken the mechanical properties of superalloys. However, the relationship between GBM and the fatigue properties of superalloys at elevated temperatures has seldom been investigated due to the difficulty in the sample preparation and experiment process. Based on six kinds of bicrystals with different tilt LAGBs made by a second-generation single-crystal superalloy, the effects of misorientation on the grain boundary microstructure and fatigue properties (980 °C) of superalloys were studied systematically in this work. It is found that, with the increase of GBM, the GB precipitates combined with the cast micropores increase monotonically, accordingly both the fatigue life and fatigue strength decrease successively. Fatigue fracture observations show that the cracks of all the bicrystals initiated from the cast micropores at GBs, and then propagated along the GBs. Therefore, the coupling effect of cast micropores and GBM on the fatigue damage mechanisms of the bicrystals are evaluated according to their hindering degrees on the piled-up dislocations. Combining with a hysteresis energy model, a quantitative fatigue strength prediction model of superalloys is established and is well verified by abundant experimental data. This study could provide guidance for fatigue performance prediction and structural design of superalloys.

关 键 词：SUPERALLOYS BICRYSTALS Grain boundary misorientation Fatigue strength Fatigue crack 

分 类 号：TG132.3[一般工业技术—材料科学与工程]