Patent ID: 7192622

Claim:
A method of masking cooling holes of a gas turbine component, the gas turbine component comprising an external surface, a cavity and a plurality of cooling holes, the method comprising the steps of (a) applying a photopolymerizable mask material substantially only to the cooling holes so that the cooling holes are at least partially filled with the mask material in the portion closest to the external surface up to the level of the external surface, the mask material containing a substance which fluoresces under ultraviolet light and, in at least a portion located at the external surface of the component, a filler material, (b) at least partially thickening at least a portion of the mask material within the cooling holes by impinging electromagnetic energy onto the mask material from outside the component, (c) carrying out an inspection using ultraviolet light to locate any unwanted 1residual mask material on the external surface of the component and removing this unwanted residual mask material from the external surface by mechanical means, (d) coating the external surface of the component and the masked cooling holes and (e) removing the remaining thickened mask material from the cooling holes, wherein (a)–(b) comprises applying the mask material in a stepwise fashion including at least partially thickening the mask material before applying a next amount of the mask material, and wherein the amount of filler contained in the mask material varies, with the mask material closest to the external surface containing a greater amount of filler.