Fatigue crack growth(FCG)behavior of 9 Cr/CrMoV dissimilar welded joint at elevated temperature and different stress ratios was investigated.Attention was paid to the region near the fusion line of 9 Cr where carbon-e...Fatigue crack growth(FCG)behavior of 9 Cr/CrMoV dissimilar welded joint at elevated temperature and different stress ratios was investigated.Attention was paid to the region near the fusion line of 9 Cr where carbon-enriched zone(CEZ)and carbon-depleted zone(CDZ)formed due to carbon migration during the welding process.Hard and brittle tempered martensite dominated the stress ratio-insensitive FCG behavior in the coarse grain zone(CGZ)of 9 Cr-HAZ.For crack near the CGZ-CEZ interface,crack deflection through the CEZ and into the CDZ was observed,accompanied by an accelerating FCG rate.Compared with the severe plastic deformation near the secondary crack in 9 Cr-CGZ,the electron back-scattered diffraction analysis showed less deformation and lower resistance in the direction toward the brittle CEZ,which resulted in the transverse deflection.In spite of the plastic feature in CDZ revealed by fracture morphology,the less carbides due to carbon migration led to lower strength and weaker FCG resistance property in this region.In conclusion,the plasticity deterioration in CEZ and strength loss in CDZ accounted for the FCG path deflection and FCG rate acceleration,respectively,which aggravated the worst FCG resistance property of 9 Cr-HAZ in the dissimilar welded joint.展开更多
基金financial support by the National Natural Science Foundation of China(No.52001200)the experimental support by Instrumental Analysis Center of SJTU。
文摘Fatigue crack growth(FCG)behavior of 9 Cr/CrMoV dissimilar welded joint at elevated temperature and different stress ratios was investigated.Attention was paid to the region near the fusion line of 9 Cr where carbon-enriched zone(CEZ)and carbon-depleted zone(CDZ)formed due to carbon migration during the welding process.Hard and brittle tempered martensite dominated the stress ratio-insensitive FCG behavior in the coarse grain zone(CGZ)of 9 Cr-HAZ.For crack near the CGZ-CEZ interface,crack deflection through the CEZ and into the CDZ was observed,accompanied by an accelerating FCG rate.Compared with the severe plastic deformation near the secondary crack in 9 Cr-CGZ,the electron back-scattered diffraction analysis showed less deformation and lower resistance in the direction toward the brittle CEZ,which resulted in the transverse deflection.In spite of the plastic feature in CDZ revealed by fracture morphology,the less carbides due to carbon migration led to lower strength and weaker FCG resistance property in this region.In conclusion,the plasticity deterioration in CEZ and strength loss in CDZ accounted for the FCG path deflection and FCG rate acceleration,respectively,which aggravated the worst FCG resistance property of 9 Cr-HAZ in the dissimilar welded joint.
