Study of phase states and oxidation of B2-structure based Al–Ni–Ru–M alloys

Phase states and oxidation resistance of B2-structure based Al–Ni–Ru–M alloys have been investigated on equilibrium alloys and by the diffusion couple approach. The isothermal cross-sections of the Al–Ni–Ru phase diagram have been partially defined in a range of Al < 70 at.% at 900 and 1100 °C. The existence of a miscibility gap between AlRu (β1) and AlNi (β2) phases in the Al–Ni–Ru ternary system has been clearly established. Experimental identifications of phase equilibria have been obtained at both temperatures, defining various phases. The high temperature properties of these alloys indicate melting points exceeding 2100 °C. The oxidation behavior of Al–Ni–Ru–M B2 alloys in air follows a parabolic law at 950 and 1050 °C and is slower than that of a commercial MCrAlY alloy. The oxidation mechanisms remain consistent with temperature, resulting in the formation of a dense protective α-Al2O3 scale. For compositions with Ru > 25 at.%, a dense continuous Ru underlayer forms between the α-Al2O3 film and the bulk alloy. The findings suggest that these alloys hold promise for use as oxidation resistant coatings in high-temperature industrial applications.