Abstract
Alloy X-750 is a precipitation-hardenable, nickel-based alloy, which contains nickel, iron, chromium, niobium, and little amount of titanium, aluminum. Since alloy X-750 was extensively applied for reactor core components, its failure may cause safety problems, and also cost loss due to replacement of components. At the present day, the research scopes of the related countries include (1) control of heat treatment and elements of alloy;(2) design of the component geometry, load and residual stresses;(2) the alternate materials. This study analyzes and characterizes the important microstructure features of X-750 for various heat treatments and evaluates stress corrosion cracking (SCC) susceptibility of alloy X-750 by the slow strain rate tensile test in different chemical environments.It was shown that the alloy X-750 suffered intergranular stress corrosion cracking (IGSCC) problem through the observation on the surface cracking of material. Alloy X-750 has the richest Cr23C6 precipitate which shows the highest resistance to IGSCC after 704℃/2Ohr aging treatment, while it has the lowest resistance to IGSCC after 885℃/24hr aging treatment. Impurity content in water chemistry can influence the resistance to IGSCC, in which the chlorine ion is more corrosive than the sulfuric ion. According to the experiment results and the related literature review, alloy X-750 shows the highest resistance to IGSCC after 704℃/2Ohr aging treatment.