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ORIGINAL RESEARCH ARTICLE

Cracking mechanism in single-pass molten pool of laser-directed energy deposition-manufactured FeCoCrNiAl high-entropy alloy coatings

Guang Zeng1 ,  Xinyu Hu1 ,  Wenjie Liu2* ,  Ke Sun3*
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1 School of Mechanical Engineering, Zhengzhou University of Aeronautics, Zhengzhou, Henan, China
2 School of Mechanical and Power Engineering, Henan Polytechnic University, Jiaozuo, Henan, China
3 School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, Hubei, China
MSAM, 026240056 https://doi.org/10.36922/MSAM026240056
Received: 14 June 2026 | Revised: 7 July 2026 | Accepted: 15 July 2026 | Published online: 6 August 2026
© 2026 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

To meet the critical strategic demands of deep-sea and polar exploration, there is an urgent need to develop a new generation of marine exploration equipment with enhanced corrosion resistance, drag reduction, and ice prevention capabilities. High-entropy alloy (HEA) coatings are an effective way to address these problems, offering excellent corrosion resistance, high mechanical properties, and drag-reduction characteristics. Laser-directed energy deposition (LDED) additive manufacturing is an advanced manufacturing technique for fabricating HEA coatings, enabling the deposition of components on complex curved surfaces while delivering excellent overall performance. However, the inherent cracking problem in LDED-processed HEAs accelerates rapid damage and coating failure. In this work, the FeCoCrNiAl HEA coatings were fabricated on the GCr18Mo substrate using LDED. The crack types and underlying cracking mechanisms, as well as crack-induced hardness degradation mechanisms, are elucidated. The results show that the defect types include solidification cracks, heat-affected zone (HAZ) cracks, and gas pores, with solidification cracks accounting for a substantial proportion. The hot stress in the molten pool exceeds the coating strength. The residual tensile stress (~ 900 MPa) in the HAZ exceeds the yield strength of the matrix, while stress fluctuations in the molten pool during solidification triggered crack initiation. The cracking mechanism is closely related to grain orientation, dislocation accumulation, and carbide. The geometrically necessary dislocation density at the crack (~ 1.33 × 1014 m−2) is higher than that in the matrix. Hard carbide particles play a critical role in crack initiation. Moreover, solidification cracks are a mixture of trans-granular and inter-granular cracks. The hardness of the molten pool, HAZ, and interface zones is higher than that of the substrate, with the HAZ exhibiting a hardness 3.53 times higher. Cracks cause a localized reduction in hardness, with the most pronounced decrease occurring in the solidification crack region. Clarifying the cracking mechanism of the LDED-manufactured HEA coatings will contribute to breakthroughs in marine engineering equipment.

Graphical abstract
Keywords
Laser directed-energy deposition
FeCoCrNiAl high-entropy alloy
Crack
Residual stress
Microstructure
Funding
This work is supported by the Henan Province Science and Technology Key Project (No.262102221023, 262102220058), the Key Scientific Research Projects of Henan Provincial Higher Education Institutions (No.26A460009, 26A460024), the Fundamental Research Funds for the Universities of Henan Province (NSFRF2602019), the Natural Science Foundation of Henan (No. 262300421411), and the Key Research and Development Projects in Henan Province (No. 261111223800).
Conflict of interest
The authors declare that they have no competing interests.
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