Effects of Ti and Y Addition on the Scale Spalling Resistance of CoNiCrAl Alloys

CoNiCrAl is usually used as the material to bond coat in thermal barrier coatings (TBC) systems under high temperatures. With different amounts of reactive elements Ti and Y added into CoNiCrAl, the effects of their adding on Al₂O₃ scale spalling resistance are ascertained by examining specimens subjected to cyclic oxidation and isothermal oxidation experiments. The results show that with the same Y content, increasing Ti to 0.3 wt% in the alloy, the scale adherence gets better; however, increasing Ti content to 0.5 wt%, the adherence goes bad. With the same Ti content, when Y in the alloy lowers from 0.4 to 0.1 wt%, the scale adherence improves. As introduced in our previous work, Ti and Y will both participate in the formation and growth of oxide peg, different sizes of oxide pegs, and the interaction between them, and reactive element will bring the different effects on the adherence of the scale.