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<p>This study investigated the effect of Hf content on the&#xa0;self-healing behavior of Al<sub>2</sub>O<sub>3</sub> films&#xa0;formed on alumina-forming austenitic (AFA) alloys under the decoking environment of petrochemical cracking process. AFA alloys with different addition of Hf (0–1&#xa0;wt%) were subjected to pre-oxidation under low oxygen partial pressure to form the initial Al<sub>2</sub>O<sub>3</sub> films. Following simulated mechanical damage, the samples underwent coking and decoking tests. The addition of Hf significantly changes the self-healing performance of the oxide film on the AFA alloy. The scratch regions of AFA alloys with 0, 0.05, and 0.25&#xa0;wt% Hf are covered with undesirable Cr<sub>2</sub>O<sub>3</sub> films. A dense and&#xa0;continuous Al<sub>2</sub>O<sub>3</sub> self-healing film formed with 0.5&#xa0;wt% Hf addition. Hf<sup>4+</sup> segregates along Al<sub>2</sub>O<sub>3</sub> grain boundaries, blocking cation diffusion channels, promoting formation of Al<sub>2</sub>O<sub>3</sub> and refining grains. Nanoscale HfO<sub>2</sub> pegs at the film/substrate interface, enhancing film adhesion. This study provides key insights for designing self-healing, coke-resistant furnace tubes with long-term performance.</p>

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Effect of Hf on the Self-Healing Property of the Alumina Film on AFA Alloy in a Decoking Environment

  • 期刊论文

  • 发表日期：

    2026年4月14日

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  • Cheng Luo,
  • Yuanbin Xiao,
  • Jin Ji,
  • Ya Liu,
  • Changjun Wu,
  • Junxiu Chen,
  • Xiangying Zhu,
  • Xuping Su

摘要

This study investigated the effect of Hf content on the self-healing behavior of Al2O3 films formed on alumina-forming austenitic (AFA) alloys under the decoking environment of petrochemical cracking process. AFA alloys with different addition of Hf (0–1 wt%) were subjected to pre-oxidation under low oxygen partial pressure to form the initial Al2O3 films. Following simulated mechanical damage, the samples underwent coking and decoking tests. The addition of Hf significantly changes the self-healing performance of the oxide film on the AFA alloy. The scratch regions of AFA alloys with 0, 0.05, and 0.25 wt% Hf are covered with undesirable Cr2O3 films. A dense and continuous Al2O3 self-healing film formed with 0.5 wt% Hf addition. Hf4+ segregates along Al2O3 grain boundaries, blocking cation diffusion channels, promoting formation of Al2O3 and refining grains. Nanoscale HfO2 pegs at the film/substrate interface, enhancing film adhesion. This study provides key insights for designing self-healing, coke-resistant furnace tubes with long-term performance.