Morphological evolution of MC carbide in K465 superalloy
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A cast nickel-base K465 superalloy is strengthened by γ′ precipitates and carbides and is intended for use as gas turbine blades and vanes operating at elevated temperature where phase alteration is prone to occur, such as carbide precipitation and degradation. Normal thermal exposure, such as experienced in processing, heat treatment or service, can alter the original structure, morphology and distribution of carbides, thereby, producing variations in the properties of the alloy [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]. For example, MC carbide can be decomposed into M6C and M23C6 carbides, and these three types of carbides may also be precipitated during the long-term thermal exposure [1, 3, 4]. In this investigation, MC carbide is emphasized.
MC carbide has blocky and script-like morphology . In addition, the chemical composition of MC carbide is very complex, including C, W, Cr, Mo, Ti, Nb and Hf. HfC is the most stable carbide compared with other types of carbides . Meantime, Ti...