Improvement of Stress Corrosion Cracking Resistance of Alloy 600 by Niobium Addition in High Temperature Water

Abstract

The effect of niobium as a stabilizing element and the effect of thermal cycles on welding of the corrosion resistance of 75%Ni-15%Cr (Alloy 600) were investigated. The results are summarized as follows:
(1) The effects of weld thermal cycle and sensitizing heat treatment on the intergranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) of Alloy 600 containing carbon more than 0.01 wt% can be explained by the behavior of chromium carbide precipitation at the grain boundaries.
(2) In Alloy 600 containing carbon more than 0.01 wt%, a suitable addition of niobium (Nb/C_??_30) prevents degradation of corrosion resistance due to the sensitization caused by the chromium carbide precipitation.