Influence of processing variables on the properties of dc magnetron sputtered NiAl coatings containing Hf additions

Abstract

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Influences of annealing and hafnium concentration on the microstructures of sputter deposited β-NiAl coatings on superalloy substrates

“…As expected, the as-deposited coatings consisted of a single layer that was conformal and adherent to the underlying substrates. This observation is consistent with the prior observations of Ning et al [18,23,24]. In some of the specimens, through thickness cracks and leader defects were observed.…”

“…The majority of the coatings exhibited strong (110) preferred orientations with weaker (211) and (220) reflections. Some of the NiAle1Hf coatings did exhibit strong (211) preferred orientations; however, in agreement with Ning et al [18,24], these differences in preferred coating orientation, when present, did not appear to alter the annealing response of the coating.…”

“…Many of the grains contained locally high dislocation densities. Interestingly, the grain sizes observed in this study were less than one third the size of those produced by Ning et al [18,24]. Lattice parameters calculated from the XRD patterns and TEM selected area diffraction patterns (Table 1) were consistent with the values for slightly off-stoichiometric NiAl published by the International Centre for Diffraction Data (ICDD) [30e32].…”

“…2 and 3 show TEM micrographs and XRD patterns collected from the as-deposited coatings. Similar to Ning et al [24], the asdeposited coatings were fine grained and single phase with ordered B2 crystal structures. Many of the grains contained locally high dislocation densities.…”

“…In this study, coatings were deposited using the sputtering parameters similar to those used by Ning et al [18,24,41] to produce NiAl-(0.1e0.6) at.% Hf coatings with zone 2 grain morphologies according to Thornton's structure zone model (SZM) [42]. However, in the present study an unbalanced magnetron configuration was used along with a higher deposition temperature (i.e., 650 C versus 400 C).…”