Behavior in cooling-induced oxide scale spallation of original and modified Cantor's HEA alloys oxidized at high temperature
Résumé
High Entropy Alloys; equimolar CoNiFeMnCr composition: Cantor Alloy
• Adding MC carbides -> increase in mechanical resistance at H.T.
• Isothermal oxidation behavior at 1000°C and 1100°C (shown today, at 2:20 PM)
– Mass gain kinetic: parabolic but …
– Very fast for the Cantor alloys and its {+MC} derivatives
– Slowed down if Mn content decreases to 10 at.% and Cr content increases to 30 at.% (but still worse than Ni–30 wt.%Cr)
• More or less protection by the external multi–constituted oxide scale
• THIS WORK: how does this complex scale behave if temperature varies?
-> first answers available in the cooling parts of the thermogravimetry curves
Increasing Mn and increasing Cr indisputably improve the resistance against scale spallation
• Difference probably due to scales not as thick as for Mn1Cr1 alloys
• But obvious lack of mechanical resistance of these multi–constituted scales
• Mn: isothermal oxidation, takes part to scales more than Cr, thus a double
deleterious effect on the scales which still exists even if %Mn is lowered
-> Remove all Mn from Cantor’s alloy derivatives destined to T ≥ 1000°C
->Testing new alloys as here and also for much faster and repeated coolings
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