Influence of force amplitude on microstructures evolution, fatigue behavior, and ratcheting failure mechanism of 1Cr18Ni10Ti pressure pipe

This paper investigates the effect of force amplitude on microstructures, fatigue behavior, and ratcheting-fatigue fracture mechanism of 1Cr18Ni10Ti pipe. Fatigue tests of non -standardized shape of pressure pipe were conducted. Microstructures were characterized by OM, SEM, and EBSD techniques. Experimental results indicated that the sample under a high -force amplitude contains a higher proportion of LAGBs, causing more prone to fracture. Cyclic softening was triggered by dislocation movements, indicating the dominant deformation mechanism of ratcheting-fatigue sample. More activated system and accumulation of dislocation density inside ferrite grains induced crack initiation. Pipe shows obvious ovalization with plastic deformation response in low -cycle fatigue fracture mode.