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Thermodynamic study, elaboration and high temperature oxidation of alloys highly strengthened by tantalum carbides. Part 2: Case of a Ni-30Cr-1C-15Ta alloy

Laura Corona, Patrice Berthod

In this second part of the present work dealing with chromium-rich alloys containing high amounts in carbon and tantalum, a Ni-30Cr-1C-15Ta alloy was elaborated by foundry, after preliminary thermodynamic calculations. These ones showed not the good nature of carbides but allowed anticipating a pro-eutectic solidification as carbides and not as matrix, as previously seen for the Co-30Cr-1C-15Ta cobalt alloy studied in the first part. The hardness of the obtained nickel alloy was rather high but a little lower than for the cobalt alloy one. Its behaviour in oxidation at high temperature was also good, with a chromia-forming character still subsisting even after 46 hours at 1150°C. Some interesting differences about as-cast microstructure, sub-surface microstructure evolution and of general behaviour in high temperature oxidation were noticed between this nickel alloy by comparison with the analogous cobalt alloy.