The effects of prior creep–fatigue on the strain rate sensitivity of a P92 welded joint

The Investigation of the Fracture Behavior of a Chinese 9% Cr Steel Welded Joint under Creep-Fatigue Interactive Loading

“…Therefore, the WM region (higher hardness) would be continuously producing inelastic strain to compensate for the local stress during the holding period. This process also results in a more remarkable reduction in the hardness of the WM region, which was observed in the previous study [10]. Therefore, the values of σ th for the welded specimens are higher than those of the BM specimens, which have homogeneous material properties.…”

“…Furthermore, the inelastic strain amplitude of the welded specimens was almost unchanged at 50% of the lifetime fraction, except the one with a 900 s holding time, which slightly decreased to 0.273%. In the previous study [10], the reduction in the hardness of the WM region was more remarkable than in the BM and FGHAZ regions, even though the WM region still had a higher value of hardness due to its high initial hardness. This reduction can be related to the Mo content in the alloy.…”

“…The peak tensile stress levels of the welded specimens were observed to increase with increasing holding time, while they remained mostly the same for all of the BM specimens. In the previous study [10], the WM region had a higher value of nanoindentation hardness than the BM and FGHAZ regions. Therefore, the average values of hardness for welded specimens were higher than those of the BM specimens.…”

“…It is well known that stress relaxation can occur in the holding period during the straincontrolled CF test [9][10][11][12]. The typical stress relaxation behavior of the welded specimens during the tensile holding period (300 s) is shown in Figure 8.…”

“…Pandey et al [8] studied the formation mechanism of various microstructures in different regions of a P92 steel welded joint and found that the welding process produced a heterogeneous microstructure in the heat-affected zone (HAZ) of the welded joint. Those regions have different sensitivities to the macroscopical CF loading [9][10][11][12]. Relying on nanoindentation, Gao et al [13] investigated the remnant creep behavior of the base metal (BM), fine-grain heat-affected zone (FGHAZ), coarse-grain heat-affected zone (CGHAZ) and weld metal (WM) for a CF-tested P92-welded joint, and they found remarkable degradations in the creep resistances of the BM and FGHAZ regions.…”