Effects of solution heat treatment on carbide of Ni-Cr-W superalloy

The microstructure features of a kind of Ni-Cr-W superalloy after solution heat treatment at different temperatures (1230-1300°C) for various time (10-120 min) were investigated by means of scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the precipitated phases of the alloy after solution heat treatment are identified as W-rich fcc M₆C and Cr-rich fcc M₂₃C₆ carbides. The volume fraction of carbides decreases with increasing of the solution heat treatment temperature and time. At the temperature above 1270°C for 120 min, most of carbides are dissolved into the Ni-matrix, and the carbides distributing at twin boundaries may be dissolved into the matrix first. M₆C carbide has no any fixed orientation relationship with the Ni-matrix, but the angle of M₂₃C₆ (220) to the matrix (13̄1) is 30°.