Evolution behavior of liquid film in the heat-affected zone of laser cladding non-weldable nickel-based superalloy

Zhenlin Zhang, Yue Zhao, Jiguo Shan, Aiping Wu, Yutaka S. Sato, Shun Tokita, Kota Kadoi, Hiroshige Inoue, Huaipeng Gu, Xin Tang

Research output: Contribution to journalArticlepeer-review

Abstract

Laser cladding with a paraxial powder-feeding device was used to repair as-cast K447A nickel-based superalloy, a kind of non-weldable alloy with a high Hf content and working as gas-turbine hot-section components. In the present study, the metallurgical evolution behavior of liquid film and liquation cracking mechanisms are studied. The results showed that a kind of uncommon Ni21Hf8 phase was found in the incipient melting regions (IMR) of the intergranular region. In the thermal cycle, γ/Ni21Hf8 eutectic liquefaction, M5B3 dissolved, and γ/γ’ eutectic liquefaction successively occurred in the heating process in IMR, and liquid → γ + γ/γ’ + M5B3 + γ/Ni21Hf8 → γ + γ’(3) + γ/γ’ + γ/Ni21Hf8 + M5B3 occurred in the cooling process. The inhomogeneity of the intergranular structure leads to the liquid film with the characteristics of discontinuous distribution and uneven width. The cracking criterion of the liquid film was established based on pressure drop. When the closed liquid film meets the condition of 2γsl<1/K*(ρsl−1*R*dt+∆hε), the liquid film with a thickness that is greater than critical thickness will be induced into a liquation cracking.

Original languageEnglish
Article number158463
JournalJournal of Alloys and Compounds
Volume863
DOIs
Publication statusPublished - 2021 May 15

Keywords

  • Grain boundaries
  • Kinetics
  • Laser processing
  • Phase transitions
  • Transition metal alloys and compounds

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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