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<p>To address the critical bottleneck regarding the service life of shield tunneling cutters subjected to extreme compound conditions—specifically fluctuating loads, corrosion, and wear—this study fabricated Ni-<i>x</i>NbC composite coatings (<i>x</i> = 0, 10, 20, 30, and 40 wt.%) on H13 steel substrates via laser cladding technology. The influence of NbC content on the microstructural evolution, mechanical properties, tribological behavior, and corrosion resistance mechanisms was systematically investigated. The results indicate that with increasing NbC content, the coating microstructure transitions from coarse columnar dendrites to uniform equiaxed grains. The partial decomposition of NbC particles in the molten pool induces the precipitation of flower-like Nb<sub>6</sub>C<sub>5</sub>, CrB, and lath-like hard phases, forming a unique nano-eutectic structure within the γ-(Fe,Ni) solid solution. The microhardness of the coatings increased by 32.1%, 54.4%, 45.6%, and 70.1% compared to the substrate, respectively. The impact and compression toughness of the coatings were recorded as 22.31, 37.24, 32.34, and 8.12&#xa0;J. Notably, the 20% NbC coating exhibited the optimal balance of strength and toughness, effectively mitigating the risk of brittle fracture caused by particle agglomeration in higher-content formulations. As the NbC content increased, the wear mechanism shifted from oxidative wear to controlled abrasive wear. Although the 40% NbC coating achieved the lowest volumetric wear rate due to its high volume fraction of hard phases, the wear resistance of the 20% NbC coating was comparable. Furthermore, the 20% NbC coating developed the most dense Nb<sub>2</sub>O<sub>5</sub>-Cr<sub>2</sub>O<sub>3</sub>-NiO composite oxide film with the highest lattice oxygen proportion, demonstrating superior Cl⁻ barrier capacity and corrosion resistance. Considering all factors, the 20% NbC coating, characterized by its uniform microstructural distribution, exceptional toughness reserve, and stable chemical shielding performance, exhibits the highest comprehensive service reliability. This coating system is identified as an ideal candidate for extreme shield tunneling conditions, providing significant technical support for extending the service life of cutters under complex operational environments.</p>

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Microstructural evolution and wear: corrosion failure behaviour of Ni–xNbC laser cladding coatings for hot-end components

  • 期刊论文

  • 发表日期：

    2026年4月22日

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  • Jingbin Hao,
  • Zhiyong Wei,
  • Hongren Liu,
  • Qin Du,
  • Haifeng Yang,
  • Hao Liu

摘要

To address the critical bottleneck regarding the service life of shield tunneling cutters subjected to extreme compound conditions—specifically fluctuating loads, corrosion, and wear—this study fabricated Ni-xNbC composite coatings (x = 0, 10, 20, 30, and 40 wt.%) on H13 steel substrates via laser cladding technology. The influence of NbC content on the microstructural evolution, mechanical properties, tribological behavior, and corrosion resistance mechanisms was systematically investigated. The results indicate that with increasing NbC content, the coating microstructure transitions from coarse columnar dendrites to uniform equiaxed grains. The partial decomposition of NbC particles in the molten pool induces the precipitation of flower-like Nb6C5, CrB, and lath-like hard phases, forming a unique nano-eutectic structure within the γ-(Fe,Ni) solid solution. The microhardness of the coatings increased by 32.1%, 54.4%, 45.6%, and 70.1% compared to the substrate, respectively. The impact and compression toughness of the coatings were recorded as 22.31, 37.24, 32.34, and 8.12 J. Notably, the 20% NbC coating exhibited the optimal balance of strength and toughness, effectively mitigating the risk of brittle fracture caused by particle agglomeration in higher-content formulations. As the NbC content increased, the wear mechanism shifted from oxidative wear to controlled abrasive wear. Although the 40% NbC coating achieved the lowest volumetric wear rate due to its high volume fraction of hard phases, the wear resistance of the 20% NbC coating was comparable. Furthermore, the 20% NbC coating developed the most dense Nb2O5-Cr2O3-NiO composite oxide film with the highest lattice oxygen proportion, demonstrating superior Cl⁻ barrier capacity and corrosion resistance. Considering all factors, the 20% NbC coating, characterized by its uniform microstructural distribution, exceptional toughness reserve, and stable chemical shielding performance, exhibits the highest comprehensive service reliability. This coating system is identified as an ideal candidate for extreme shield tunneling conditions, providing significant technical support for extending the service life of cutters under complex operational environments.