Designing a new family of high temperature wear resistant alloys based on Ni3Al IC: experimental results and thermodynamic modelling

A new family of IC based alloys termed ‘Nicralc’ was proposed as a substitute for high temperature abrasion and erosion resistant cobalt alloys. The new alloy family presents microstructures containing hard chromium carbides dispersed in a continuous γ′(L12), Ni–Al–Cr ordered intermetallic matrix. Alloy design aimed at matrix compositions similar to IC-221, with chromium and carbon added. Modelling of the Ni–Al–Cr–C phase diagram was undertaken using ThermoCalc calculations. A customized thermodynamic database (NICRALC) assembled from different databases was used to calculate the liquidus, solidification sequence and equilibrium phases of compositions near the γ′+carbide field. The solidification sequence was studied experimentally using DTA, OM and SEM, X-ray diffraction of sections and of extracted carbides. Different carbide structures were obtained, depending on the composition. Hypoeutectic alloys presented γ′/γ dendrites and interdendritic eutectic γ′+carbide. Hypereutectic alloys presented a bi-modal carbide distribution, with large proeutectic carbides within a fine γ′+carbide matrix, suitable for producing in situ composites by directional solidification.