Microstructure and property analysis of DC magnetron sputtered NiAl–0.6Hf coatings

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.…”

“…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].…”

“…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.…”

Preparation of Ni-Aluminide Surface Layer Containing Hafnium by Molten-Salt Electrodeposition and Cyclic-Oxidation Resistance

“…It was reported that the addition of a small amount of Hf into the Ni aluminide is effective for improving the spallation of the Al 2 O 3 scale on the Ni aluminide. 2,3) It was suggested that the suppression of the Al 2 O 3 scale spallation due to the addition of a small amount of Hf resulted from the key-on effect of scale, 8) the void absorption in the scale/metal interface 9) and the improvement of plastic deformation of the scale. 10) Figure 8 shows cross-sectional micrographs and concentration profiles of Ni, Al, Cr, Hf and O in the specimens with Ni aluminide layers formed by the (a) process, for which the electrodeposition time of Hf was 1.8 ks, after the cyclic oxidations of (a) 2 cycles, (b) 5 cycles and (c) 10 cycles.…”

“…2,3) We already succeeded in the forming of Ni aluminide layer containing small amounts of Y by the stepwise electrodeposition of Y, Ni and Al on the Ni-base alloy and improved the cyclic-oxidation resistance of the Ni-base alloy. 4) In the present study, the forming of a Ni aluminide layer containing small amounts of Hf by the stepwise electrodeposition of Hf, Ni and Al on the Ni-10 at%Cr-8 at%Al alloy was attempted.…”