Internal and External Protection of Gas Turbine Blades by Slurry Silicoaluminizing Process

External and internal surfaces of the blade airfoils are exposed to the gas turbine operating environment, which is both thermally and chemically hostile. Diffusion ahlminide coatings are particularly useful for providing environmental protection to components equipped with internal cooling passages because they are able to provide environmental protection without significantly reducing the cross-sections of the coolingpassages. In this study. slwry method was utilized to apply plain aluminide and Si-modified ahlminide coatings onto external and internal surfaces of Ni-base super alloys of In738LC and GTD-l11. The thicknesses of applied coatings onto external and internal sample surfaceswere 70-90 um and 30-60 um, respectively. The microstructures ofthe coatings have been investigated using SEM. EDS, XRD and. TEM. The examinations showed that the Al-Si coating is an intermetallic nickel aJllminjde coating with a siliconenriched outer layer that contains silicide precipitates. The intermetallic phase was formed by an inward diffusion of aluminum. Based on the XRD results obtained. it was found that the Al-Si coatings with sufficient silicon promote the formation of some SiCh oxides in conjunction with AhO] and results in improving the oxidation resistance of ahlminide coatings.

Internal and External Protection of Gas Turbine Blades by Slurry Silicoaluminizing Process Keywords:

blade , coolingpassage , slurry , silicon , aluminizing , cyclic oxidation