Effect of melt heat treatment on MC carbide formation in nickel-based superalloy K465

Abstract

The morphology of MC carbide has been observed to vary with melt heat treatment (MHT) temperature in K465 nickel-based superalloy, which had been remelted in a DTA instrument. MC carbide transforms from block-type morphology to script-type morphology when the MHT temperature increases from 1360 °C to 1400 °C, and the size of MC carbide colonies are reduced with the MHT temperature further increased to 1450 °C. A liquid metal X-ray diffractometer was utilized to detect the variation of melt structure which was induced by increasing of MHT temperature. And the exothermic curves were recorded by the DTA instrument to identify the solidification process of the melt with different melt structure. The morphology of dendrite arms, the solidification process and the melt structure prior to solidification were all employed to clarify the mechanism of MC carbide morphology transformation. Keywords: Nickel-based superalloy, Melt structure, Solidification process, Nucleation and growth, Multicomponent solidification