In this work, the microstructure evolution and fracture mechanism of a novel 9% chromium tempered martensite ferritic steel G115 were investigated over the temperature range of 625–675 °C using uniaxial creep tests. The creep curves consist of a primary transient stage followed by an apparent secondary stage, and an accelerated tertiary creep regime. The relationship between the minimum creep rate and the applied stress followed Norton's power law. Based on the EBSD analysis, there were no obvious textural features formed after creep deformation, and with the increase in creep time, the number of subgrains slightly increased, and then sharply increased, indicating dynamic recrystallization (DRX) occurs after creep deformation. In addition, three types of precipitates can be observed after creep deformation: W-rich Laves phase, Nb-rich MX, and Cu-rich precipitates. The Nb-rich MX with a square shape and Cu-rich precipitates with an ellipsoidal shape remain very stable. However, the W-rich Laves phases distributed mainly on the grain boundaries have rod-like, chain-like, and bulky shape, which are coarsened significantly. Representative fractographs of the G115 steel after creep deformation exhibit significant necking with an elliptical shape. A dense array of deep and equiaxed dimples appear in the central region under the tested creep conditions. Ductile fracturing is the dominant fracture mechanism during short-term creep deformation.

在这项工作中，使用单轴蠕变试验研究了新型9％铬回火马氏体铁素体钢G115的组织演变和断裂机理。蠕变曲线包括一个主要的瞬态阶段，一个明显的次级阶段和一个加速的第三蠕变状态。最小蠕变率与外加应力之间的关系遵循诺顿幂定律。根据EBSD分析，蠕变变形后没有形成明显的组织特征，并且随着蠕变时间的增加，亚晶粒的数量略有增加，然后急剧增加，表明蠕变变形后发生了动态再结晶（DRX）。此外，蠕变变形后可以观察到三种类型的沉淀物：富W的Laves相，富Nb的MX，富含铜的沉淀物。方形的富Nb MX和椭圆形的富Cu沉淀物保持非常稳定。但是，主要分布在晶界上的富W Laves相具有棒状，链状和大体积的形状，其被粗化。G115钢的蠕变变形后的代表性分形仪显示出明显的椭圆形颈缩。在测试的蠕变条件下，在中心区域会出现密集的深凹和等轴凹窝阵列。延性断裂是短期蠕变变形过程中的主要断裂机制。明显变粗了。G115钢的蠕变变形后的代表性分形仪显示出明显的椭圆形颈缩。在经过测试的蠕变条件下，密集的深凹和等轴凹窝阵列出现在中心区域。延性断裂是短期蠕变变形过程中的主要断裂机制。明显变粗了。G115钢的蠕变变形后的代表性分形仪显示出明显的椭圆形颈缩。在经过测试的蠕变条件下，密集的深凹和等轴凹窝阵列出现在中心区域。延性断裂是短期蠕变变形过程中的主要断裂机制。