The use of Cr-Ni austenitic steel interlayers is an effective solution for heterogeneous welds, especially in combination with high-carbon steels. High contact-fatigue resistance and resistance to impact loads are required in the case of railway crossing applications. The failure of Nb-alloyed cast Cr-Ni austenitic steel used as an insert in the flash butt resistance weld of Hadfield steel with carbon steel is the subject of the presented analyses. The identification of the failure mechanism is based on light and scanning electron microscopy and energy dispersive X-ray analyses, including electron backscattered analyses. The initiation of hot-crack defects is detected in the heat affected zone (HAZ). In contrast to the usual conditions for the formation of hot cracks in the HAZ, cracks are found solely outside the superheating zone. The decisive influence of Nb-based intermetallics formed at the phase interface of δ-ferrite and the austenitic matrix is indicated. The eutectics formation between niobium carbonitrides and the austenitic matrix is assumed to be responsible for the hot-cracking susceptibility of austenitic steel. The particular combination of the temperature gradient together with the chemical gradient leading to a localization of the critical zone is documented. The paper describes the influence of carbon redistribution at the weld interface on the morphology of delta-ferrite in different layers of the heat-affected zone. Induced structural differences are associated with Nb-particle formation. Fractographic analyses show the formation of low-melting phases in the critical layer of the HAZ. The influence of secondary phases, especially Nb-eutectic, on the degradation of austenitic steel plasticity is documented.

Cr-Ni奥氏体钢中间层的使用对于异质焊缝是一种有效的解决方案，尤其是与高碳钢结合使用时。在铁路道口应用中，要求具有较高的接触疲劳强度和耐冲击载荷性能。本文所研究的主题是，哈德菲尔德钢与碳钢的耐闪光对接焊缝中嵌入的Nb合金铸造Cr-Ni奥氏体钢的失效。失效机理的识别基于光和扫描电子显微镜以及能量色散X射线分析，包括电子反向散射分析。在热影响区（HAZ）中检测到热裂纹缺陷的产生。与在热影响区中形成热裂纹的通常条件相反，仅在过热区之外才发现裂纹。指出了在δ铁素体和奥氏体基体的相界面处形成的Nb基金属间化合物的决定性影响。碳氮化铌与奥氏体基体之间的共晶形成被认为是造成奥氏体钢热裂敏感性的原因。记录了温度梯度与化学梯度一起导致临界区局部化的特定组合。本文描述了热影响区不同层中焊缝处碳的再分布对δ-铁素体形态的影响。诱导的结构差异与Nb粒子的形成有关。分形分析表明，在热影响区的关键层中形成了低熔点相。次生相的影响，尤其是Nb共晶，