Abstract
The growth kinetics of protective diffusion aluminide coatings were investigated on Ti based alloy Beta-21S. The coating was prepared by halide activated pack cementation using CrCl3 as transport agent and pure aluminum (high activity) as masteralloy. The coating was composed of only TiAl3 layer whose growth was controlled by solid state diffusion following a parabolic law. The morphology of the coating was quite similar with interdiffusion products present in a bulk semi-infinite diffusion couple as showed by previous literature studies. The transport phenomena are significantly affected by the alloying elements present in the alloys and dissolved in the coating layer. The activation energy estimated at 108 kJ mol−1 determined for temperatures in the range 660-760 °C, indicates a bulk diffusion process with a possible grain boundary contribution and/or kinetic limitations associated to the mobility of the gaseous species during the aluminization.
Published Version
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