Abstract
AR and CHT heat treated alloy 718 have been studied for stress corrosion cracking in the high temperature NaC1 solution. The influence of grain boundary precipitates on the SCC resistance is discussed. Most amcunt of precipitate were found in CHT heat treated specimen by SEM metallography. There were Laves phase, delta (δ) phase and MC carbide in CHT heat treated specimen by XRD analysis, diffraction pattern, bright field and dark field image of delta (δ) phase were identified by TEM. The slow strain rate test results showed that stress corrsion cracking were not found for both AR and CHT heat treated speciments in high temperature (150℃~288℃) NaC1 (0.1M~2.0M) solution. More amount of precipitates like Laves, delta (δ) and MC carbide phase were probably the reason that carsed CHT heat treated specimen with wores mechanical properties compared with AR heat treated specimen.