Coupling effects of tungsten and molybdenum on microstructure and stress-rupture properties of a nickel-base cast superalloy

作     者：Tongjin Zhou Wei Feng Huibin Zhao Yu Meng Huaxia Zhang Hongsheng Ding Zichen Wang 

作者机构：National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of Technology Beijing Institute of Aeronautical Materials 

出 版 物：《Progress in Natural Science:Materials International》 (自然科学进展·国际材料(英文))

年 卷 期：2018年第28卷第1期

页      面：45-53页

核心收录：

学科分类：08[工学] 080502[工学-材料学] 0805[工学-材料科学与工程（可授工学、理学学位）] 

主　　题：Superalloy Tungsten and molybdenum Cast Microstructure Stress-rupture properties 

摘      要：In order to comprehensively understand the forming mechanism of abnormal phases solidified in a nickel-base cast superalloy with additives of tungsten and molybdenum, the coupling effects of W and Mo on the microstructure and stress-rupture properties were investigated in this paper. The results indicated that the precipitation of primary α-（W, Mo） phase depended tremendously on the amount of W and Mo addition. When the total amount of W and Mo was greater than 5.79 at%, α-（W, Mo） phase became easily precipitated in the *** increasing of Mo/W ratio, the dendrite-like α-（W, Mo） phases were apt to convert into small bars or blockylike phases at the vicinities of γ′/γ eutectic. The morphological changes of α-（W, Mo） phase can be interpreted as the non-equilibrium solidification of W and Mo in the alloy. Since the large sized α-（W, Mo） phase has detrimental effects on stress-rupture properties in as-cast conditions, secondary cracks may mainly initiate at and then propagate along the interfaces of brittle phases and soft matrix. During exposing at 1100 ℃ for 1000 h, the α-（W, Mo） phases transformed gradually into bigger and harder M;C carbide, which results in decreasing of stress-rupture properties of the alloy. Finally, the alloy with an addition of 14W-1Mo（wt%） maintained the longest stress lives at high temperatures and therefore it revealed the best microstructure stability after 1100 ℃/1000 h thermal exposure.