The influence of ternary additions of W, Mo, Ti, Ta, and Nb on the isothermal and cyclic oxidation of Ni-10Cr alloy

Abstract

Isothermal and cyclic oxidation studies have been carried out on Ni-10Cr binary alloy and ternary alloys containing respectively 8.0 wt.% Mo, 14.3 wt% W, 4.2 wt.% Ti, 7.7 wt.% Nb, and 14.1 wt.% Ta (i.e., ∼5 at.%, respectively). Tests were carried out for a total duration of 100 hr at 1000°C in a flowing simulated flue gas mixture apportioned to 81 vol. % N₂, 16 vol. % O₂, and 3 vol. % CO₂. Various cycling frequencies were used in the thermal cycling studies. Alloys containing Ta (especially) and Nb behaved better during both isothermal and cyclic oxidation, while additions of Mo and W resulted in poor oxidation properties and spallation, especially at higher cycling frequencies. Self-healing oxides rich in Cr were found to be significant in the former cases, there being some benefit to be derived from Ta- or Nb-containing oxides. Ti which was of benefit isothermally was of little use under cyclic conditions.