Characteristics and resistance against spallation of the oxides formed at high temperature on {Co, Ni}-based chromium-rich cast alloys containing titanium - Archive ouverte HAL Accéder directement au contenu
Poster De Conférence Année : 2022

Characteristics and resistance against spallation of the oxides formed at high temperature on {Co, Ni}-based chromium-rich cast alloys containing titanium

Résumé

Titanium is a MC carbide–forming element which can be used to obtain carbides, in addition to other carbides or as single carbide present. These carbides are able to take part to the interdendritic mechanical reinforcement for resisting stresses at high temperature. However, titanium can strongly react with oxygen or nitrogen. Consequently its presence may influence the general behavior of chromia–forming alloys in oxidation at high temperature, by promoting the formation of other oxides than chromia. In this work, a series of samples all containing 25 wt.%Cr, 0.4wt.% C and 1.6wt.%Ti, with a base element shared between nickel and cobalt in various proportions, were exposed at 1250°C during 70 hours with mass gain recording. The variation of mass during a -5°C min-1 cooling was monitored also using the thermo–balance and the oxidized states and deteriorated sub-surfaces after return to room temperature were characterized. The nature of the interdendritic carbide network precipitating at the end of solidification is dependent on the base element: Co favors TiC and Ni favors chromium carbides. Over 70 hours at 1250°C the global oxidation rate is influenced neither by the base element, nor by the form with which titanium is present in the alloy (as TiC carbides or as solute in the matrix); however, catastrophic oxidation threatens the cobalt–richest alloy earlier than the other alloys. Thank to the 25 wt.%Cr contained by the alloys, all of them are chromia–forming, at least up to 50 hours. Titanium is involved in internal oxidation but an outermost TiO2 layer formed at the top of the chromia scale, particularly in the case of the nickel–richest alloys (phenomenon related to a higher mobility of Ti when not trapped in TiC carbides?) Does the outermost TiO2 layer proctect the chromia scale against volatilization?
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Dates et versions

hal-04547571 , version 1 (15-04-2024)

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Paternité - Pas d'utilisation commerciale - Pas de modification

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  • HAL Id : hal-04547571 , version 1

Citer

Synthia Annick Ozouaki Wora, Patrice Berthod. Characteristics and resistance against spallation of the oxides formed at high temperature on {Co, Ni}-based chromium-rich cast alloys containing titanium. Eurocorr 2022 : European Corrosion Congress, Aug 2022, Berlin (Germany), Germany. ⟨hal-04547571⟩
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