High-temperature creep rupture behavior of dissimilar welded joints in martensitic heat resistant steels

Significant reduction in creep life of P91 steam pipe elbow caused by an aberrant microstructure after short-term service

“…Our study of aberrant P91 steel indicates that the cavity size produced under low temperature and high stress conditions is smaller than that under high temperature and low stress conditions. However, other works of literature have demonstrated that increasing stress 10 , reducing temperature 9 , and exposure time 14 also result in greater cavity growth rates and coalescence, which leads to larger size and smaller number density of cavities. Stress, temperature, and exposure time directly determine the cavity formation for normal P91 steel.…”

“…Figure 10 d further confirms that the Laves phase cluster along the PAGBs with a large area, and the linear size within the visual range was close to 3.4 μm. The precipitates preferentially nucleate at PAGBs, lath boundaries, and subgrain boundaries 10 , 11 . Due to the loss of the lath boundary and the decrease of subgrain boundaries for aberrant P91 steel in this study, a cluster of Laves phase precipitates at PAGBs.…”

“…At the same time, the absence of martensitic lath boundaries may also result in abnormal growth of the Laves phase. Under operating temperature, the high coarsening rate of the Laves phase leads to the loss of the early positive effect of precipitation-strengthening during the early creep process 10 and reduces the solid solution strengthening 11 . If the creep life deterioration caused by the aberrant structure directly affects the safe operation of the power unit, and the nuclear or thermal power plant operators will face a safety risk.…”

“…If the creep life deterioration caused by the aberrant structure directly affects the safe operation of the power unit, and the nuclear or thermal power plant operators will face a safety risk. Therefore, the creep life prediction of critical components, especially those with aberrant mis-heat treated conditions, needs to be carefully assessed for the sake of safe operation of power plants 10 , 12 , 13 .…”

“…In addition, some literature results have shown that increasing stress 10 , reducing temperature 9 , and prolonging exposure time 14 may also lead to accelerated cavity growth rates and coalescence, resulting in large-sized cavities and smaller number density of voids. The cavity formation in normal P91 steel is determined by stress, temperature, and exposure time.…”