Abstract
CoNiCrAl alloys are widely employed as a high temperature resistant material in thermal barrier coating (TBC) systems. In such materials, the adherence between the thermally grown oxide (TGO) Al2O3 scale and the alloy is strengthened by oxide pegs formed by dispersed oxide addition or the oxidation of doped reactive elements. In this study the addition of Ti as the reactive element to a CoNiCrAlY alloy has been addressed. We investigated the mutual effects between Ti and the oxide pegs in alloy samples that had been subjected to a cyclic oxidation process. The alloy with a higher Ti content exhibited a uniformly fine β-phase and fewer voids at the scale/alloy interface, the scale growth rate was lower for Ti-containing alloys. In addition, the formation and growth of oxide pegs led to an irregular distribution of Ti in the scale and at the scale/alloy interface, which resulted in local variations in the features of the scale, with fewer voids and a thinner scale at the sites that are far from the oxide pegs. Meanwhile, the incorporation of Ti to the Y-rich oxide led to an increase in the bonding strength between the peg core and the Al2O3 sheath.
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