After long-term service, boat samples of 1Cr-1/2Mo steel seemed to have aged, evidenced by the spheroidisation of carbides in the pearlite region, and a dispersion of fine M23C6 precipitation in the ferrite matrix. The yield strength of the cracked boat samples was two to three times the reported values of new A387 Grade 12 Class 2 material. The ductility is less than 0.5 times the reported values of the new grade. The intergranular fracture mode was likely due to the fine carbide precipitation inside the ferrite grains that strengthened the metal matrix, and the coarse intergranular CrMo-rich carbides that weaken the precipitate/grain boundary interfaces. Cavities similar to creep were observed along the grain boundaries in some of the boat samples, suggesting a possible creep-oxidation damage mechanism for coke drum steels.

中文翻译：

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服役暴露的1Cr-1/2Mo焦炭鼓钢的显微组织老化和性能退化

在长期使用后，1Cr-1/2Mo 钢的船形样品似乎已经老化，这可以通过珠光体区域中碳化物的球化以及铁素体基体中细小的 M23C6 析出物来证明。裂纹船样品的屈服强度是新 A387 12 级 2 级材料报告值的两到三倍。延展性小于新牌号报告值的 0.5 倍。晶间断裂模式可能是由于铁素体晶粒内部的细小碳化物析出强化了金属基体，而粗大的富含 CrMo 的晶间碳化物削弱了析出物/晶界界面。在一些船样品中沿晶界观察到类似于蠕变的空腔，表明焦炭鼓钢可能存在蠕变氧化损伤机制。