This study investigates cracking and healing behavior during the oxide scale formation on high-carbon steel. The steel was heated to 1000°C at a rate of 2°C/s in the air atmosphere. The surface morphology of the oxide scale was monitored in situ using Laser Scanning Confocal Microscopy (LSCM) and oxide phases in the scale were analyzed by X-ray diffraction (XRD). The microstructures of scale cross-sections were analyzed by Electron Probe Micro-analysis (EPMA). Based on the surface morphology of the oxide scale at different temperatures, we established a relationship between blistering and the “state” of the oxide scale. Blistering occurs during the scale growth due to the decarburization process, since evolved gaseous products cause swelling and eventual rupturing of the oxide scale, forming cracks on the surface. Thermal stress induced by the difference in FeO/Fe₃O₄ thermal expansion coefficients causes crack expansion. Subsequent crack healing consists of the following steps: (1) oxygen penetrates the oxide scale through the cracks and reacts with FeO to form Fe₃O₄. This reduces the difference in the thermal expansion coefficients and decreases the thermal stress, restraining the crack expansion; (2) at a certain temperature, the oxidation rate increases and oxygen reacts with the substrate to form new oxides, which fill in the formed blisters. The mechanism of crack expansion and healing was developed by monitoring the evolution of oxide scale morphologies during the blistering process.

本研究调查了高碳钢氧化皮形成过程中的开裂和愈合行为。将钢在空气气氛中以 2°C/s 的速率加热到 1000°C。原位监测氧化皮的表面形貌使用激光扫描共聚焦显微镜 (LSCM) 和 X 射线衍射 (XRD) 分析水垢中的氧化物相。通过电子探针显微分析（EPMA）分析鳞片横截面的微观结构。根据不同温度下氧化皮的表面形貌，我们建立了起泡与氧化皮“状态”之间的关系。由于脱碳过程，在氧化皮生长过程中会发生起泡，因为释放出的气态产物会导致氧化皮膨胀并最终破裂，从而在表面形成裂纹。FeO/Fe ₃ O ₄差异引起的热应力热膨胀系数导致裂纹扩展。随后的裂纹愈合包括以下步骤： (1)氧气通过裂纹渗透氧化皮并与FeO反应形成Fe ₃ O ₄。这减小了热膨胀系数的差异，降低了热应力，抑制了裂纹扩展；(2)在一定温度下，氧化速率增加，氧气与基材反应生成新的氧化物，填充形成的气泡。通过监测起泡过程中氧化皮形态的演变，开发了裂纹扩展和愈合的机制。