A study of the diffusional response of refractory and other elements in superalloy systems during diffusion coating

Samples of commercially pure nickel and two common superalloys were prepared by electroplating a thin layer of platinum on the surface, then exposing the samples to temperatures of 950°C and 1080°C for periods of two and six hours. Using electron probe micro analysis (EMPA), elemental composition profiles were obtained from the samples following the diffusion steps. The relative diffusion coefficients for a number of elements were determined using a classical Boltzmann–Matano method. As expected, it was discovered that elements such as cobalt, chromium, titanium and tantalum displayed a significant diffusional response in this relatively short time, while tungsten, molybdenum and rhenium diffused to a lesser degree under these conditions. It was discovered that there is significant interaction between many of the alloying elements in these systems during the diffusion anneal. The limitations of the analytical technique are summarized.