Abstract
The effect of grain boundary precipitation on the environmental behavior of Inconel 718 was determined. The performance of conventionally heat treated (CHT) material was compared with that of direct-aged (DA) material. Straining electrode tests with cathodic polarization at room temperature and fatigue tests in aqueous environments ranging from 30 to 288 C were performed. Microstructurally, direct aging was found to reduce the size and amount of grain boundary precipitates significantly. A decrease in the amount of grain boundary precipitation results in a reduction of grain boundary cavitation and an increase in ductility during straining electrode tensile tests. Grain boundary cavitation does not affect tensile properties in air. However, cathodic polarization during tensile testing significantly embrittles the CHT condition relative to the DA condition. Direct aging does not affect fatigue crack growth rates in aqueous environments at temperatures ranging from 30 to 288 C.
