Abstract: Thermal machines operating under high temperatures, thermal gradients and mechanical efforts typically, are build from Ni based alloys. Aluminizing will enhance oxidation resistance due to the formation of NiAl Beta layer that acts as a reservoir of Al and favors alpha alumina scale. Aluminizing can be applied on thermal spray intermediate layers, used to enhance thermal compatibility. This research contributes to understanding of variables that can affect the oxidation behavior. Influence of porosity and oxides content of thermal spray coatings on pack aluminizing surfaces, using in and above the pack procedures were investigated. A Ni based alloy was sprayed and coatings aluminized at 1100ºC under argon gas flow. Results reveals that aluminizing procedures determine the microstructure of coatings and oxide scale features. A higher porosity induces a nonuniform distribution of Al across the lamellar sprayed coating . In the pack processing resulted on thicker coatings and the sintering of lamellar structure.
Authors: Valéria Donati Silvério, Irene Bida de Araujo, Ingrid Fogaça, and Ana Sofia C.M. d’Oliveira
Keywords: Pack aluminizing, Ni alloys, thermal spray coatings, microstructure