Field-evaporation of {0 0 1} planes and site occupancy of Pt in β-NiAl

In order to improve the high-temperature oxidation resistance of Ni based superalloy components for aeroengines and gas turbines, Pt-modified aluminide diffusion coatings are often used. However, no detailed models explaining the influence of Pt on the microstructural development of the coating during heat treatment have been reported. The main reason for this is the limited amount of thermodynamical and diffusion data for the ternary Ni–A1–Pt system. The aim of this study is to determine the site occupancy of 1 at.% Pt in solid solution in stoichiometric β-NiAl by means of atom probe analysis. The analysis was performed along the 〈0 0 1〉 direction of the specimen in order to resolve the pure {0 0 1} Ni and Al planes, respectively. It was found that Pt was distributed evenly on the Al and Ni sites. Further statistical analysis (Stacked Profile method) indicated a very slight preference to Al sites. Also some results on the field-evaporation behaviour of {0 0 1} Ni and Al planes were achieved. Ion trajectory aberrations at the {0 0 1} pole and at zone lines were observed and compared with previous findings and computer simulations for similar materials.