The effect of the growth mode of the pre-diffused layers on the microstructure of aluminide coatings modified by titanium or silicon for gas turbine hot-section applications

Aluminide coatings are great importance in protecting hot-section gas turbine components. Study the effects of pre-diffused layer on the final microstructure and properties of coating is useful in better exploiting of aluminide coatings potential. In this investigation the results of microstructural studies of modified aluminide coatings with pre-diffused titanium or silicon layers was presented and compared with a co-deposited titanium-modified aluminide coating and simple aluminide coating. It was found that silicon diffusion layer grows inwardly and increases the final aluminide coating thickness more than twice of the simple aluminide coating. About half of the silicon-modified aluminide coatings consisted the brittle Ni2Al3 phase. In contrast, titanium diffusion layer grew outwardly and didn’t have a considerable effecton the final thickness, but dilutes the areas close to the coating surface from alloying elements. This effect may be considered beneficial to the hot corrosionbehavior of the coating via the basic fluxing mechanism.