热等静压超高压容器用36CrNi3MoVA钢疲劳性能及微观组织机制研究OA

The shortage of low-cycle fatigue data of 36CrNi3MoVA steel applied to 200 MPa grade wire-wound hot isostatic pressing vessels under stress amplitudes of 0～586 MPa is targeted,and fatigue tests and multi-scale microstructural characterizations are carried out in this work.Dumbbell-shaped specimens are subjected to cyclic loading by an electro-hydraulic servo fatigue testing machine under 1 Hz sinusoidal loading,and the fatigue behaviors and microstructural mechanisms of the material are analyzed.It is indicated by test results that no fracture is generated on specimens within 15 000 cycles,and a remarkable extension of fatigue life is observed with the reduction of stress amplitude from S-N curves.All cracks are found to initiate at surface micro-defects by SEM/EDS detection;clear fatigue striations are observed in crack propagation zones,and cleavage characteristics are presented in instant fracture zones.Uniform element distribution without segregation is verified by energy spectrum analysis.Nanoscale carbides inside grains and at grain boundaries are discovered by TEM observation,and dislocations are pinned by such carbides through the bypass mechanism to stabilize tempered martensite microstructures.No fatigue-induced phase transformation is detected by Raman spectroscopy.A positive correlation between the area ratios of crack initiation zones,crack propagation zones and fatigue life is confirmed by confocal measurements,and surface quality is identified as the key factor dominating fatigue life.A hierarchical inspection strategy oriented to RBI is put forward on the basis of test results,which includes outer wall ultrasonic guided wave inspection,inner wall phased array inspection and residual life prediction based on fracture mechanics.Data support and theoretical basis are supplied for regular scientific inspection and quantitative risk evaluation of HIP vessels.