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<p>To address the poor thermal shock resistance of conventional Cr<sub>3</sub>C<sub>2</sub>-NiCr coatings (CC) on copper molds subjected to extreme thermal cycling, a nano-modified multimodal Cr<sub>3</sub>C<sub>2</sub>-NiCr coating (NMC) was fabricated via HVOF spraying on CuCrZr substrates. Its hierarchical microstructure integrated nano-, submicron-, and micron-sized Cr<sub>3</sub>C<sub>2</sub> particles within a NiCr matrix, strengthened by nano-CeO<sub>2</sub>-induced lattice distortions and rare-earth enrichment. Compared to CC, NMC reduced porosity by 77.2% (0.33% versus 1.45%) and increased adhesion strength by 65.6% (75.24 versus 45.44&#xa0;MPa). Thermal shock resistance was systematically evaluated through water-quenching tests at 550-750&#xa0;°C, and crack propagation behaviors were analyzed via SEM/EDS. The results revealed that NMC extended lifetime by 2.2 × at 750&#xa0;°C (77 cycles versus 35.67 cycles for CC), 2.0 × at 650, and 1.5 × at 550&#xa0;°C, maintaining localized spallation without catastrophic delamination. Microstructural analyses demonstrated that NMC’s strong interlayer cohesion promoted vertical crack propagation with nonlinear paths, where crack tips underwent deflection, branching, and arrest at ultrafine-grained regions. In contrast, CC exhibited early crack nucleation at internal defects and lamellar interfaces, forming interconnected horizontal and vertical crack networks that accelerated spallation. The superior performance of NMC is attributed to the synergistic effects of its multimodal architecture (crack-arresting) and nano-CeO<sub>2</sub> solid-solution strengthening (reduced thermal mismatch and enhanced cohesion). These findings highlight the potential of NMC for applications demanding superior thermal shock resistance and mechanical integrity under rapid thermal cycling, with future work focusing on industrial-scale optimization and long-term service validation. </p>

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Thermal Shock Resistance and Crack Propagation Behaviors of Nano-modified Cr3C2-NiCr Coatings with Multimodal Architecture

  • 期刊论文

  • 发表日期：

    2025年8月19日

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  • Chenxi Shi,
  • Ming Hu,
  • Irfan,
  • Shibin Liu,
  • Qinglin Gong

摘要

To address the poor thermal shock resistance of conventional Cr3C2-NiCr coatings (CC) on copper molds subjected to extreme thermal cycling, a nano-modified multimodal Cr3C2-NiCr coating (NMC) was fabricated via HVOF spraying on CuCrZr substrates. Its hierarchical microstructure integrated nano-, submicron-, and micron-sized Cr3C2 particles within a NiCr matrix, strengthened by nano-CeO2-induced lattice distortions and rare-earth enrichment. Compared to CC, NMC reduced porosity by 77.2% (0.33% versus 1.45%) and increased adhesion strength by 65.6% (75.24 versus 45.44 MPa). Thermal shock resistance was systematically evaluated through water-quenching tests at 550-750 °C, and crack propagation behaviors were analyzed via SEM/EDS. The results revealed that NMC extended lifetime by 2.2 × at 750 °C (77 cycles versus 35.67 cycles for CC), 2.0 × at 650, and 1.5 × at 550 °C, maintaining localized spallation without catastrophic delamination. Microstructural analyses demonstrated that NMC’s strong interlayer cohesion promoted vertical crack propagation with nonlinear paths, where crack tips underwent deflection, branching, and arrest at ultrafine-grained regions. In contrast, CC exhibited early crack nucleation at internal defects and lamellar interfaces, forming interconnected horizontal and vertical crack networks that accelerated spallation. The superior performance of NMC is attributed to the synergistic effects of its multimodal architecture (crack-arresting) and nano-CeO2 solid-solution strengthening (reduced thermal mismatch and enhanced cohesion). These findings highlight the potential of NMC for applications demanding superior thermal shock resistance and mechanical integrity under rapid thermal cycling, with future work focusing on industrial-scale optimization and long-term service validation.