Creep and Oxidation Behaviors of 25 wt.% Cr–Containing Nickel-Based Alloys Reinforced by ZrC Carbides

Abstract

Three alloys based on nickel, rich in chromium due to their oxidation resistance at high temperature and containing ZrC carbides for their mechanical reinforcing against creep, were elaborated by foundry. After control of their as-cast microstructures, these alloys were subjected at 1100 °C to flexural creep and to oxidation in air. Script-like ZrC carbides were obtained in the interdendritic spaces, forming a eutectic compound with a part of the matrix. One of the alloys additionally contained Cr7C3 eutectic carbides. By comparison with a Ni–Cr–C reference alloy with similar contents in Cr and C, the three alloys demonstrated a much better creep resistance for the same conditions of stress and temperature. However, their oxidation rates were much greater than for the reference alloy. In contrast with the chromia-forming reference alloy, several kinds of oxides formed in the case of the three alloys, as NiCr2O4 spinel and oxides involving zirconium. A significant inward interdendritic oxidation progression was noticed for the three studied alloys. To benefit from the interesting creep resistance of these alloys for long sustainability in service, it appears necessary to significantly improve their oxidation behavior.