Electron microscopy study of laser welded GH909 superalloy joint

Journal of Materials Research and Technology

Gaoyang Mi¹  Chunming Wang¹  Xiuquan Ma²  Zhengwu Zhu² 

[1] School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China;School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China;

关键词: GH909 superalloy;    Laser welding;    Solidification sequence;    Eutectic constituents;   

DOI  :  

来源: DOAJ

【 摘 要 】

The formation process of gamma/Laves eutectic constituents were systematically investigated in both heat-affected zone (HAZ) and fusion zone (FZ) of laser-welded GH909 superalloy. Solidification sequences and eutectic reactions were proposed by morphologically and chemically analyzing phase and chemical composition by utilizing various characterization methods. In FZ, the ultimate eutectic constituents experienced three stages: 1) liquid (L)→Primary gamma (γ) (1360 °C), forming a γ dendritic morphology; 2) following L→γ+(Nb, Ti)C precipitation at mushy zone; 3) terminal L→γ+Laves (1184 °C) at γ interdendritic regions. Enrichment of Nb in Laves and surrounding γ produced a high dislocation density in eutectic constituents. Continuous distribution of such γ/Laves structures promoted the formation of micro interdendritic solidification cracks under accumulated tensile stress. In HAZ, however, the fraction of γ/Laves constituents was heat input depended and increased as the reduction of distance from fusion line. An interactionally and simultaneously integrated process NbC+γ→Laves (~1323 °C) caused the formation of eutectic constituents with NbC decomposition, Laves formation, grain boundary liquation and subsequently eutectic reactions.

【 授权许可】

Unknown