Effect of ternary elements on a martensitic transformation in β-NiAl

A diffusion-multiple method was applied to determine the effect of nine ternary elements (Pt, Ta, Cr, Mo, Re, W, Zr, Si, and Co) on the martensitic transformation in β-NiAl. The results show that martensite formation is highly sensitive to composition, temperature, and kinetics. Electron microprobe analysis was employed to establish the composition of the ternary martensitic regions on the diffusion multiples. With the exception of Pt, Cr, and Co, the solubility limits of the ternary additions in β-NiAl were low (less than ∼2 at%) and the elements with the highest solubilities, Pt and Co, appeared to substitute predominantly with Ni. The implications of the aforementioned ternary additions are also discussed with regards to the overall performance of NiAl-based thermal barrier coating bond coat alloys.