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<p>The high-temperature oxidation resistance of CrAlN coatings is synergistically regulated by aluminum content and temperature, but the atomic-scale mechanism of the initial oxidation stage remains unclear. This study combines ab initio molecular dynamics (AIMD) simulations with experiments to systematically investigate the effects of aluminum content (Cr<sub>0.5</sub>Al<sub>0.5</sub>N and Cr<sub>0.15</sub>Al<sub>0.85</sub>N) and temperature (773&#xa0;K, 973&#xa0;K, and 1173&#xa0;K) on the oxidation mechanism of the coatings. Simulation results indicate that Cr<sub>0.5</sub>Al<sub>0.5</sub>N preferentially form a dense (Cr, Al)<sub>2</sub>O<sub>3</sub> mixed oxide layer at high temperatures, with Cr–O–Al bonding dominating during the initial oxidation stage, effectively inhibiting oxygen diffusion, while in Cr<sub>0.15</sub>Al<sub>0.85</sub>N, aluminum atoms selectively migrate to form discontinuous Al<sub>2</sub>O<sub>3</sub> layers, resulting in only a small amount of (Cr, Al)<sub>2</sub>O<sub>3</sub> mixed oxide layers, thereby reducing the protective efficacy against oxidation. By analyzing the average displacement of oxygen atoms bonded to metal atoms (Cr, Al), it is found that high temperatures (1173&#xa0;K) significantly accelerate metal atom migration, promoting the densification of mixed oxides in Cr<sub>0.5</sub>Al<sub>0.5</sub>N. At the same time, CrAlN-1 (Cr<sub>0.54</sub>Al<sub>0.46</sub>N) and CrAlN-2 (Cr<sub>0.17</sub>Al<sub>0.83</sub>N) coatings were prepared. The results indicate that at 1173&#xa0;K (900&#xa0;°C), CrAlN-1 forms a denser oxide layer of 0.3&#xa0;μm primarily consisting of (Cr, Al)<sub>2</sub>O<sub>3</sub>, whereas CrAlN-2 develops a thicker oxide layer of 0.45&#xa0;μm dominated by Al<sub>2</sub>O<sub>3</sub> with minor (Cr, Al)<sub>2</sub>O<sub>3</sub> content. The XPS analysis confirmed that as the temperature increased, the CrAlN-1 coating formed more Cr–O–Al bonds with better oxidation resistance. The experimental results are consistent with the simulation calculations, verifying the feasibility of predicting the anti-oxidation performance of coatings using ab initio molecular dynamics methods, and providing a theoretical basis for the design of high-performance CrAlN coatings.</p> Graphical abstract

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Oxidation behavior of CrAlN: ab initio molecular dynamics simulations and experiments

  • 期刊论文

  • 发表日期：

    2025年10月9日

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  • Ergeng Zhang,
  • Jingjing Xu,
  • Biao Huang,
  • Qiong Zhou,
  • Qiang Chen,
  • Dandan Liang,
  • Zhibin Lou

摘要

The high-temperature oxidation resistance of CrAlN coatings is synergistically regulated by aluminum content and temperature, but the atomic-scale mechanism of the initial oxidation stage remains unclear. This study combines ab initio molecular dynamics (AIMD) simulations with experiments to systematically investigate the effects of aluminum content (Cr0.5Al0.5N and Cr0.15Al0.85N) and temperature (773 K, 973 K, and 1173 K) on the oxidation mechanism of the coatings. Simulation results indicate that Cr0.5Al0.5N preferentially form a dense (Cr, Al)2O3 mixed oxide layer at high temperatures, with Cr–O–Al bonding dominating during the initial oxidation stage, effectively inhibiting oxygen diffusion, while in Cr0.15Al0.85N, aluminum atoms selectively migrate to form discontinuous Al2O3 layers, resulting in only a small amount of (Cr, Al)2O3 mixed oxide layers, thereby reducing the protective efficacy against oxidation. By analyzing the average displacement of oxygen atoms bonded to metal atoms (Cr, Al), it is found that high temperatures (1173 K) significantly accelerate metal atom migration, promoting the densification of mixed oxides in Cr0.5Al0.5N. At the same time, CrAlN-1 (Cr0.54Al0.46N) and CrAlN-2 (Cr0.17Al0.83N) coatings were prepared. The results indicate that at 1173 K (900 °C), CrAlN-1 forms a denser oxide layer of 0.3 μm primarily consisting of (Cr, Al)2O3, whereas CrAlN-2 develops a thicker oxide layer of 0.45 μm dominated by Al2O3 with minor (Cr, Al)2O3 content. The XPS analysis confirmed that as the temperature increased, the CrAlN-1 coating formed more Cr–O–Al bonds with better oxidation resistance. The experimental results are consistent with the simulation calculations, verifying the feasibility of predicting the anti-oxidation performance of coatings using ab initio molecular dynamics methods, and providing a theoretical basis for the design of high-performance CrAlN coatings.

Graphical abstract