Study on SCC Susceptibility of Inconel X-750 in High-Temperature Pure Water: Effects of Aging Temperature and Time

Abstract

Abstract The stress corrosion cracking (SCC) behavior of Inconel X-750 in high-temperature water has been examined in relation to aging conditions. SCC susceptibility for the two-step (solutioning + aging), heat-treated alloy (SA) varied with its aging condition, and the aging conditions that gave a high yield strength also gave a high SCC susceptibility. Wide chromium depletion produced by the formation of M23C6 along the grain boundary during aging was identified by energy dispersive x-ray analysis (EDXA) to be a cause of intergranular stress corrosion cracking (IGSCC) susceptibility for SA. The three-step (solutioning + stabilizing + aging), heat-treated alloy (SSA) was more susceptible to IGSCC than the SA alloy, in spite of the smaller corrosion rate in a modified ASTM Standard G-28 test. EDXA revealed titanium segregation and formation of titanium-rich phases along the grain boundary, and it is speculated that the poor resistance to IGSCC following a SSA treatment might be caused by formation of a l...