The initiation of intergranular failure in inconel-600

Abstract

The nature of slip interaction with the grain boundaries was examined on the polished surface of Inconel-600 pulled in tension at 370°C and at the initial strain rate of 1.65 × 10⁻⁶ sec⁻¹. It was shown that the grain boundaries could not always accommodate slip taking place at the boundary regions. This led to the separation of grains at the boundary. Depending on the detailed morphology of the carbides, these intergranular cracks could form at axial strains as low as 10 pet. Since the cracking takes place in the inert atmosphere, it is concluded that the grain boundaries are inherently embrittled by the formation of carbides and/or by solute segregation. There was no evidence of grain boundary sliding, but when carbides were absent highly localized slip in the boundary region gave the appearance of grain boundary offsets. The implications of these observations to stress corrosion cracking are discussed.