HAZ Liquation Cracking Mechanism of IN-738LC Superalloy Prepared by Laser Solid Forming

Jianjun Xu, Xin Lin, Yufan Zhao, Pengfei Guo, Xiaoli Wen, Qiuge Li, Haiou Yang, Hongbiao Dong, Lei Xue, Weidong Huang

科研成果: 期刊稿件文章同行评审

80 引用 (Scopus)

摘要

The heat-affected zone (HAZ) liquation cracking mechanism of nickel-based superalloys with high (Al+Ti) content during the laser solid forming (LSF) process was investigated via laser remelting of an as-deposited IN-738LC superalloy. Microstructural HAZ analysis revealed that cracks consistently propagated from the HAZ to the remelting zone along the grain boundary (GB). The formation of a liquid film during GB liquation was mainly owing to localized melting of the semicontinuous γ-γ′ eutectic distributed along the GB. The solute segregation behavior of the IN-738LC alloy during LSF was analyzed using the Giovanola–Kurz model and Scheil models, revealing that a significant enrichment of γ-γ′ eutectic-forming elements in the residual liquid at the final stage of solidification (solid fraction ~ 0.87) in the molten pool was the main cause of semicontinuous γ-γ′ eutectic formation along the GB. Further, a B enrichment at the GB was identified in LSF-fabricated IN-738LC, which promoted cracking by lowering the GB liquation temperature and promoting wetting of the GB by the liquid film. Unlike the phenomenon observed in the welding of cast IN-738LC, the coherence between the γ′ phases and the γ matrix in LSF-fabricated IN-738LC can suppress the occurrence of constitutional liquation of the γ′ phase. To understand the interaction between the thermal stress and the liquid film in the LSF process, thermal stress as a cracking driving force was also estimated based on the measurement of the residual stress from the substrate to the remelting zone of the IN-738LC deposit by the Vickers micro-indentation method.

源语言英语
页(从-至)5118-5136
页数19
期刊Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
49
10
DOI
出版状态已出版 - 1 10月 2018

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