Aluminide coatings were applied by halide activated pack cementation to austenitic 304 stainless steel substrates. The evolution of coating microstructure as a function of coating process parameters, e.g., temperature, time, etc., was explored. Stainless steel type 304 was chosen as a model substrate to understand the kinetics of aluminizing and for the potential enhancement in high temperature corrosion resistance. The kinetics of the aluminizing process was studied at different temperatures in the 650 – 850°C range and times in the 1 – 25 h range. At 650°C, the coating consisted of a single layer containing two phases tentatively identified as Al5FeNi (Cr) as the matrix with a dispersed aluminide, Al86Fe14. At 850°C, the coatings initially consist of at least two layers containing three phases [with a preliminary identification as Al86Fe14, AlxFey(Ni,Cr) and Al5Fe Ni(Cr) which transitions to a single layer of possibly AlxFey(Ni,Cr) and intermetallic precipitates of undetermined composition.

Subject
X-ray diffraction, Nickel coatings, Steel surfaces, Protective coatings, Coatings, Substrates, Precipitates, Diffusion, Aluminum, Coating thickness, Aluminides, Stainless steel, Samples
Keywords:
Coatings, pack cementation, aluminizing, stainless steel, corrosion
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2012
Association for Materials Protection and Performance (AMPP)
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