Influence of severe plastic deformation and subsequent annealing on creep behaviour of martensitic 9% Cr steel

Petr KRÁL, Jiri DVOŘÁK, Václav SKLENIČKA, Zenji HORITA, Yoichi TAKIZAWA, Yongpeng TANG, Lenka KUNČICKÁ, Květa KUCHAŘOVÁ, Marie KVAPILOVÁ, Marie SVOBODOVÁ
2021 METAL 2021 Conference Proeedings   unpublished
The objective of the study is to evaluate the effects of severe plastic deformation (SPD) and annealing on creep behaviour of advanced tungsten modified creep-resistant 9 % Cr martensitic P92 steel. The as-received P92 steel was deformed by high-pressure torsion (HTP), high-pressure sliding (HPS) and rotary swaging (RS) at room temperature prior creep testing. These SPD methods imposed significantly different equivalent plastic strain in the range from 1 up to 20. Constant load creep tests in
more » ... nsion were performed in an argon atmosphere at 873 K and applied stress ranging from 50 to 200 MPa. The microstructure and phase composition of P92 steel were studied using a scanning electron microscope Tescan Lyra 3 and a transmission electron microscope Jeol 2100F. The results show that under the same creep loading conditions the HPT and HPS-processed P92 steel exhibited significantly faster minimum creep rates, creep fracture strain and the decrease in the value of the stress exponent of the creep rate in comparison with as-received P92 steel. However, it was revealed that the RS-processed specimens exhibited one order of magnitude lower minimum creep rate and lower ductility compared to commercial P92 steel. The creep curves for the HPT and HPS-processed states exhibited a pronounced minimum of strain rate. The pronounced minimum of strain rate disappeared when these states were annealed at 923K/500h before application of creep loading. The microstructure changes occurring during creep and different creep behaviour between as-received and deformed states are discussed.
doi:10.37904/metal.2021.4147 fatcat:hv3drakcdbayde7bzj5ladwese