Effect of Al and Ti addition on the characteristics of oxide inclusions in Ni-based superalloy

The characteristics of inclusions have a significant influence on the performance and fatigue life of Ni-based alloy and some cracks usually initiate and propagate from inclusions. High-temperature experiments were carried out at 1823 K to study the effect of Al and Ti addition on the characteristics of oxide inclusions in Ni-based alloy. The size, number, distance, distribution of oxide inclusions and degree of homogeneity in inclusion dispersion in Ni-based alloy with [%Al](i) = 0.3-0.7 and [%Ti](i) = 0.7-1.2 (i represent initial addition of deoxidant) were analyzed systematically. It is found that the oxide inclusions in alloys with [%Al](i) = 0.7, [%Ti](i) = 0.7/1.2 had smaller average size of 2.4 mu m and distributed more homogeneously. The Ostwald ripening theory and collision model were applied to point out the relationships among compositions of Ni-based alloy, behaviors of oxide inclusions and their characteristics under the condition of no external stirring. The calculated results were in good agreement with experimental results. The mechanism on obtaining fine and dispersed oxide inclusions in Ni-based alloy was summarized.