Insights into the SCC crack tip of Alloy 690TT in caustic solution at high temperature

摘要

The SCC crack tip of deformed Alloy 690TT tube was investigated in high temperature caustic solution. The results showed that SCC crack tip extended along the oxidation zone on the grain boundaries. The oxidation zone was composed of mixed oxides including NiO, Ni, spinel oxide and Cr2O3. Due to the competitive effect of intergranular carbides and local deformation zone (LDZ) on diffused oxygen, the oxidation zone ahead of crack tip bypassed the carbides as branched oxide and then grew up to be nodular oxidation zone, which resulted in a semi-continuous nodular pattern for the oxidation zone along the crack. (C) 2021 Elsevier B.V. All rights reserved.