Abstract: A low-cycle fatigue property test is conducted on the test piece of welded rotor made by 25Cr2Ni2MoV material. The relation of strain and fatigue life is measured and the low-cycle fatigue properties of different joint zones are contrastingly researched. The heat affected zone is the relatively weak part of welded joint on low-cycle fatigue property. Researches of matrix hardness distribution of welded joint, fatigue crack propagation path and auger electron component analysis of element segregation at original austenite grain boundary of heat affected zone are conducted. The results show that soft zone and interface of hard and soft appear in the heat affected zone, which makes it suffer big strain concentration and reduced low-cycle fatigue property under fatigue load. In heat affected zone, the fatigue crack propagation path is likely to deflect along the original austenite grain boundary and separate the boundary to some extent. Through AES analysis, obvious element segregation of S and Cr are found at the original austenite grain boundary of heat affected zone, which weakens the resistance of fatigue crack propagation of this zone and degrades the low-cycle fatigue property of the whole weldment.

Key words: grain boundary segregation, hardness distribution, heat affected zone, low-cycle fatigue, weldment