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Abstract <p>The influence of a production method (hot rolling, electron beam additive manufacturing (EBAM)) and subsequent heat treatment on the microstructure and corrosion resistance of a KhN62M nickel alloy (composition (wt %): 23–24 Cr, 12–14 Mo, ≤0.75 Fe, Ni for balance) in a molten salt of the 3LiCl–2KCl eutectic composition at a temperature of 650°C is studied. Hot-rolled samples are characterized by an equiaxed polycrystalline structure with an average grain size of ~150 μm and a developed network of intergranular boundaries. Some of the EBAM samples are subjected to heat treatment, namely, water quenching from 1120°C. The formation of intermetallic phases (presumably σ phase) and their role in protecting the material from corrosion damage are shown. Microstructural analysis (scanning electron microscopy with energy dispersive spectroscopy, SEM/EDS) has revealed the following key differences: EBAM samples in the as-built state have a pronounced dendritic microstructure with chemical segregation of elements (Cr, Mo) and secondary phases, which are localized in interdendritic regions and form via layer-by-layer growth during deposition. This structure decreases the corrosion rate due to the formation of microgalvanic couples, where intermetallic phases act as local anodes, dissolving protectively and limiting the spread of corrosion in the dendritic matrix. Subsequent heat treatment of the EBAM samples leads to the dissolution of these protective phases and structural homogenization, which causes a decrease in corrosion resistance. In contrast, hot-rolled samples demonstrate significantly higher corrosion activity. This is associated with a developed network of intergranular boundaries, which serve as paths for accelerated diffusion and centers for the development of intergranular corrosion. Selective leaching is confirmed by chromium depletion in the surface layers of the alloy. The obtained data, which establish a direct link between manufacturing technology, microstructure, and corrosion behavior, open prospects for a targeted use of additive technologies to create corrosion-resistant nickel alloys with improved performance characteristics in high-temperature aggressive media, such as halide melts.</p>

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Influence of a Production Method and Heat Treatment on the Microstructure and Corrosion Behavior of a KhN62M Nickel Superalloy in a Molten LiCl–KCl Salt

  • 期刊论文

  • 发表日期：

    2025年8月1日

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  • E. A. Bel’tyukov,
  • R. R. Alimgulov,
  • A. Yu. Zhilyakov,
  • D. V. Pyrin

摘要

Abstract

The influence of a production method (hot rolling, electron beam additive manufacturing (EBAM)) and subsequent heat treatment on the microstructure and corrosion resistance of a KhN62M nickel alloy (composition (wt %): 23–24 Cr, 12–14 Mo, ≤0.75 Fe, Ni for balance) in a molten salt of the 3LiCl–2KCl eutectic composition at a temperature of 650°C is studied. Hot-rolled samples are characterized by an equiaxed polycrystalline structure with an average grain size of ~150 μm and a developed network of intergranular boundaries. Some of the EBAM samples are subjected to heat treatment, namely, water quenching from 1120°C. The formation of intermetallic phases (presumably σ phase) and their role in protecting the material from corrosion damage are shown. Microstructural analysis (scanning electron microscopy with energy dispersive spectroscopy, SEM/EDS) has revealed the following key differences: EBAM samples in the as-built state have a pronounced dendritic microstructure with chemical segregation of elements (Cr, Mo) and secondary phases, which are localized in interdendritic regions and form via layer-by-layer growth during deposition. This structure decreases the corrosion rate due to the formation of microgalvanic couples, where intermetallic phases act as local anodes, dissolving protectively and limiting the spread of corrosion in the dendritic matrix. Subsequent heat treatment of the EBAM samples leads to the dissolution of these protective phases and structural homogenization, which causes a decrease in corrosion resistance. In contrast, hot-rolled samples demonstrate significantly higher corrosion activity. This is associated with a developed network of intergranular boundaries, which serve as paths for accelerated diffusion and centers for the development of intergranular corrosion. Selective leaching is confirmed by chromium depletion in the surface layers of the alloy. The obtained data, which establish a direct link between manufacturing technology, microstructure, and corrosion behavior, open prospects for a targeted use of additive technologies to create corrosion-resistant nickel alloys with improved performance characteristics in high-temperature aggressive media, such as halide melts.