High temperature properties of several chromium-containing Co-based alloys reinforced by different types of MC carbides (M=Ta, Nb, Hf and/or Zr)

Patrice Berthod (1)

1 INPL - Institut National Polytechnique de Lorraine

Five cast cobalt alloys based on Co-8Ni-30Cr-0.4/0.45C and containing Ta, Nb, Hf and/or Zr were studied by metallography in the as-cast condition and after treatments at 1300°C. The obtained MC carbides were all interdendritic with a eutectic script-like morphology. For similar carbon contents, the HfC carbides are the most developed in the as-cast microstructure and the most stable at 1300°C. As-cast, the TaC carbides are less developed than the former and they tend to become more fractioned and less present in microstructure at 1300°C. The NbC carbides, which have initially the same morphology and the same fraction as TaC, rapidly dissolve at 1300°C. The cobalt alloys containing HfC or TaC are chromia-forming at 1300°C. The NbC-containing alloy catastrophically oxides after only few hours at 1300°C. The average hardness is the highest for the HfC-containing alloy and the lowest for the NbC-containing alloy.

Mots clés: High temperature alloys (A); Microstructure (C); Oxidation (C); Thermal analysis (D); Scanning electron microscopy (D)

Domaines: Matériaux

Patrice Berthod. High temperature properties of several chromium-containing Co-based alloys reinforced by different types of MC carbides (M=Ta, Nb, Hf and/or Zr). Journal of Alloys and Compounds, 2009, 481, pp.746 - 754. ⟨hal-02166449⟩