Effect of carbides on the creep properties of a Ni-base superalloy M963

Effect of carbides on the creep properties of a cast Ni-base superalloy M963 tested at 800 and 900 °C over a broad stress range has been investigated. Correlation between the carbides and creep properties of the alloy is enabled through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). During high temperature creep tests, the primary MC carbide decomposes sluggishly and a large amount of secondary carbides precipitate. The cubic and acicular M6C carbide precipitates at the dendritic core region. Extremely fine chromium-rich M23C6 carbide precipitates preferentially at grain boundaries. The M6C and M23C6 carbides are found to be beneficial to the creep properties of the alloy. At lower temperature (800 °C), the interface of MC carbide with matrix is one of the principal sites for crack initiation. At higher temperature (900 °C), the oxidation and the precipitation of μ phase are the main factors for significant loss in creep strength of the alloy.