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Hafnium carbides in cast chromium-rich refractory alloys. Part 2: Case of cobalt-based alloys

Patrice Berthod

In this second part of a work dealing with the microstructure effect of hafnium in chromium-rich refractory alloys in presence of carbon, cobalt alloys were considered. Several weight percents of Hf were added to {Co- 25Cr}-based alloys also containing 0.25 and 0.50wt.% of carbon. This led to the development of interdendritic HfC carbides forming a eutectic with the matrix, instead chromium carbides. The same behaviour as previously seen in the first part of this work about nickel alloys was then found again. As in the later alloys the repartition and morphology of these HfC carbides let think to good mechanical resistance at room temperature as well as at high temperature. Hardness at ambient temperature is enhanced by the presence of these HfC carbides, by comparison with the chromiumcarbides existing in the same alloys in absence of Hf and also by comparison to HfCcontaining nickel alloys of similar compositions.