Research on Multiaxial Creep Properties of P92 Steel Based on Improved KR Creep Constitutive Model

In this paper, the multiaxial creep test under the action of internal pressure tensile composite load is carried out, the equivalent stress of 15 MPa internal pressure, 130 MPa equivalent stress, and the fracture experiment with 2% equivalent strain under the same conditions are carried out. Observation of structure and fracture morphology, research on multiaxial creep fracture mechanism and damage evolution law. The research results show that: under the action of the equivalent force and the first principal stress bar, the multiaxial creep process curve under the internal pressure is closer to the equivalent force, the first principal stress bar. The multiaxial creep process under the action of the first principal stress strip, and the multidirectional stress promotes the damage development of the material. After observing the metallographic structure at each stage of creep, we found that as the creep process proceeds, in the microscopic creep structure, the grain size is getting larger and the number of precipitates is also increasing. The more, and the changes that occur in the early stages of creep are small and cause little damage to the material; while in the later stages, the changes are larger and the failure rate is faster.