V. T. Burtsev.
ABSTRACT:
The deoxidation of nickelEbase superalloys upon vacuum melting was carried out in the presence of Al with strong deoxidizers such as La and Ce. The oxygen activity (a[O]) in the Ni–O–Al (0.001–5%), Ni–O–La/Ce (0.001–0.1%) and Ni–O–Al (5%)–La/Ce (0.001–0.1%) melts at 1560°C and PAr = 0.1 MPa has been studied by the method of instantaneous EMF recording by certified sensors. For the former two melting systems, the a[O] = f[Al/La/Ce%] dependences are described by logarithmic functions. The deoxidizing ability of Ce in the second system is higher by a factor of 4.7 than that of La. For the melts of the third system, the a[O] = f[Al (5%)–La/Ce] dependences constructed in the “spline” regime showed that the introduction of La (0.02–0.05%) decreases a[O] by a factor of 6–8 relative to the data on the second system of melts, and the introduction of Ce (0.02–0.05%) decreases a[O] by a factor of 3–3.4 relative to the data on the second system of melts, and the deoxidizing capacity of Ce remains higher than that of La in the presence of aluminum. Therefore, Ce is preferable as the final oxidizer in the practice of deoxidation.
KEYWORDS:
Nickel-oxygen-aluminum melts, lanthanum, cerium, EMF method, deoxidation
DOI: 10.7868/S0235010618050043