高速列车1Cr17Ni2制动杠杆螺栓沿晶开裂机理研究

高速列车用1Cr17Ni2马氏体不锈钢制动杠杆螺栓在服役过程中发生脆性沿晶开裂。通过断口观察、腐蚀产物成分分析、力学性能测试、微观组织分析和验证试验，揭示该螺栓的开裂机理。制动杠杆螺栓沿晶开裂的原因主要来自两个方面:内因是第二类回火脆性使Cr元素在晶界偏聚，并在晶界上生成"串珠状"含Cr第二相粒子，导致晶界强度下降；外因是螺栓在服役过程中受到了具有较大应变速率的外力的作用。此外，裂纹萌生的位置表明，应力集中在制动杠杆螺栓开裂过程中扮演了重要角色。

Intergranular Cracking Mechanism of 1Cr17Ni2 Brake Lever Bolt in High-speed Train

Intergranular cracking occurred to a brake lever bolt of 1Cr17Ni2 martensitic stainless steel in a high-speed train. The cracking mechanism was studied by fracture observation, corrosion products analysis, mechanical tests, microstructure observation and verification tests. The results show that the intergranular cracking of the bolt mainly resulted from two aspects. The internal cause is that the grain boundary strength was weakened because of the segregation of Cr element on the grain boundary caused by the unreasonable tempering treatment and the generation of the bead-like second-phase Cr-containing particles on the grain boundary. The external cause is that the bolt was under the external force with high strain rate during service. Furthermore, the crack initiation position revealed that stress concentration also played an important role in cracking of the brake lever bolt.