M.C. Galetz, X. Montero, M. Schütze
in "Proceedings of Corrosion 2014", NACE (2014), C2014-4105
Aluminization of turbine blades has been successfully applied for some decades to protect turbine blades from rapid oxidation. In the last years, new developments showed that the enrichment of surfaces with certain elements by diffusion heat treatments can be very well tailored according to the requirements stipulated by the base substrate used as well as the corrosive environment and thereby widely extend the application range of diffusion coatings.
A fine tuning of the chemical composition can be of high value, whether it is to achieve a good compliance in the coefficients of thermal expansion (CTE) between the substrate and the coating or be it to modify the diffusion coatings by certain elements that highly retard corrosion by changing the mechanisms of coating degradation. Another interesting field where progress has been made is the better understanding of application processes such as pack cementation or slurry route, which allows a better control of the manufacturing. The phases, which will occur on the material surface after pack cementation as well as their thickness, can be very well predicted beforehand and thus the coating can be designed according to the requirements.
To understand the mechanisms during the diffusion of slurry coatings has simplified their processability and made a manufacturing route in air possible.
An overview on such developments will be given in this work.