Comparison of the oxidation behavior of β and γ-γ′ NiPtAl coatings

This study compared the oxidation behaviors of gamma-gamma ' NiPtAl coatings and traditional beta-phase NiPtAl bond coatings. Both types of NiPtAl coatings were fabricated on two different single-crystal Ni-base superalloys using the same source of electroplated Pt. Characterization of the coating composition and alumina scale morphology after cyclic oxidation in dry oxygen at 1150 degrees C indicated that the addition of Ti in one superalloy had affected the scale microstructure and had degraded scale adhesion on the gamma-gamma' coating. In general, the alumina scale formed was thicker on the gamma-gamma'-coated substrates, and those coatings contained a larger number of pores, thought likely to be primarily due to a Kirkendall-type effect. (C) 2009 Elsevier B.V. All rights reserved.