Formation of aluminide coatings on Ni and austenitic 316 stainless steel by a low temperature FBCVD process

The experimental formation of aluminide coatings on 316 stainless steel grades and Ni by use of a chemical vapour deposition via the fluidised bed technique at relatively low temperatures (550, 560 and 570 °C for the steel and 550–650 °C for Ni) was studied. A mathematical model that predicts the growth rate of the coating for both substrates is being proposed. The experimental results were evaluated by means of optical microscopy. Uniform coatings even for reduced treatment times of a few minutes were produced. The measured coating thickness was compared to the predicted results from the model. The results indicate a linear correlation of coating thickness and treatment time for short treatment times and a parabolic correlation for longer ones. The low treatment temperature allows for energy saving and the mechanical properties of the treated parts remain unaffected.