Oxidation and Microstructural Behaviors at 1200 °C of 32.5 wt.% Cr–Containing Co–Based Alloys Strengthened by HfC Carbides

Abstract

Two alloys based on cobalt, designed to be reinforced by HfC and containing chromium with content beyond 30 wt.%, were produced by casting. They were subjected to a 46 h–long isothermal exposure at 1200 °C in synthetic air with thermogravimetric monitoring of the oxidation progress. In the as–cast state, the two alloys contain high quantities of script–like shaped HfC carbides. Both of them demonstrated a much better behavior than previous similar alloys containing only 25 wt.% Cr. After 46 h at 1200 °C, the morphology of the carbides had almost not evolved. The control of the creep behavior at 1200 °C showed that these oxidation–resistant alloys are, additionally, as creep–resistant as the 25 wt.% Cr containing previous alloys.

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

“…Zr is more available and cheaper than hafnium, and such alloys ought to be bases for alternative superalloys. Future work may first concern the understanding of the deleterious role of Zr for the oxidation behavior, as well as obtaining a real chromia-forming behavior, by increasing the chromium content beyond 30 wt.%, for instance (as successfully tested for HfC-strengthened Co-based alloys [29]).…”