Abstract
Creep rupture behavior of dissimilar weldments between FB2 and 30Cr1Mo1V heat-resistant steel by multipass welding at 783 K (510°C) under different stresses (260 to 420 MPa) was researched. The fitted creep rupture exponent is 14.53, and the 10,000 h extrapolating strength values predicted by the power law and Larson-Miller parameter show good agreement with experimental data. The samples exhibit a ductile fracture character and fracture in the weld fusion zone, which has a highly heterogeneous microstructure and grains with different morphologies and sizes and an obvious softening. There exist a decrease in the dislocation and precipitate density and an increase in the subgrain size in the weld metal after creep. The rupture is a transgranular fracture characterized by dimples as a result of microvoid coalescence. Laves phases along with copper-rich precipitates are observed in the vicinity of fracture surface, which creates a stress concentration that can cause transgranular fracture initiation.
Highlights
With the purpose of reducing carbon dioxide emissions which cause increasingly serious environmental pollution and meeting increasing demand on energy, research on renewable green energy is needed on the one hand; traditional ultrasupercritical (USC) generation technology with improved steam parameters like higher temperature and pressure has developed rapidly in recent decades on the other hand [1,2,3]
According to Ref. [8] which studied the P91/P22 weld joint, the fracture was initiated in P22 parent material at relatively low temperatures and high stresses while fracture occurred in the weld metal at higher temperatures and lower stresses
The weld fusion zone changes from the maximum hardness region to the minimum during creep testing, which is more obvious for the regions on the side near the fusion boundary, indicating that a softening phenomenon occurs in weld metal
Summary
With the purpose of reducing carbon dioxide emissions which cause increasingly serious environmental pollution and meeting increasing demand on energy, research on renewable green energy is needed on the one hand; traditional ultrasupercritical (USC) generation technology with improved steam parameters like higher temperature and pressure has developed rapidly in recent decades on the other hand [1,2,3]. Dissimilar metal welding techniques have been gradually utilized to manufacture many important mechanical parts in industry, such as thermal power rotors in USC unit or large petrochemical pressure vessels like reactor and separator in petrochemical industry, since dissimilar welding applications have the advantages like unique property combinations, weight reductions, lower costs, and improved energy efficiency [4]. A great amount of researches [6,7,8,9,10,11,12,13] have been implemented to assess the creep deformation and fracture behavior of dissimilar weld joints of creep-resistant steels. Dagmar [12] researched the precipitates quantitatively in weld joints of COST F and FB2 creep-resistant steels with conventional and accelerated creep tests, and the fracturing was located in HAZ of the F steel. Creep resistance of similar and dissimilar weld joints of P91 steel
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