The microstructure evolution and its effect on creep behaviors in P92 steel under different stresses

In this study, uniaxial creep tests of P92 steel at 650 degrees C were carried out at the different applied stresses in the range of 90-125 MPa to study the microstructure evolution and its effect on the corresponding creep behaviors of P92 steel under different stresses. The results revealed that different laws of hierarchical martensite structure and precipitates evolution, as well as their different interaction mechanisms with dislocations, resulted in different creep behaviors at different stress levels. Under the high applied stress (>90 MPa), slightly coarsened martensite laths and precipitates led to the formation of high-density dislocation cells in the martensite laths and pile-ups on lath boundaries. With the decrease of the applied stress, significant coarsening of precipitates at the packet/block boundaries led to the disappearance of the fine packets/blocks, and the subgrains gradually formed in the martensite laths. Under high applied stress, the disappearance of martensite structure and creep cavities initiated at ultrafine grains zones and inclusion/matrix interface accelerated creep to enter the tertiary stage. Under low applied stress (90 MPa), the coarsening of martensite laths, as well as cavities caused by interaction between coarsened precipitates and high-angle grain boundaries accelerated creep to enter the tertiary stage.

Automated summary

In this study, uniaxial creep tests were conducted on P92 steel at 650 degrees C under different applied stresses. The microstructure evolution and its effect on the corresponding creep behaviors were investigated. It was found that different stress levels resulted in different creep behaviors due to the evolution of hierarchical martensite structure and precipitates, as well as their interaction with dislocations.