Aircraft gas turbine blade and vane repair in superalloys

The high replacement costs of aircraft gas turbine blades and vanes have created a fast-growing, highly-specialized segment of the aircraft repair industry. The economic rationale for repair in lieu of replacement is prima facie. The metallurgical rationale is less certain, but satisfactory flight performance over the past twenty-five years at least attests to the technical adequacy of blade and vane repairs. Blade repairs, other than re-coating, generally consist of weld overlays on low-stress blade tip or tip shroud locations. On average, high-pressure turbine blades undergo two repair cycles before replacement. Low-pressure turbine blades similarly require repair but are replaced less frequently. Dimensional restoration of a subtly distorted component to demanding original equipment standards is a real engineering challenge. Coating technology is an equally sophisticated aspect of blade repair. Vane repairs are more avant-garde ranging from platform dimensional restoration to complete airfoil replacement. Vane airfoil crack repair is commonplace and involves a multiplicity of metallur.gical processes many of which are still maturing. The future of blade and vane repair, like the past, will be determined by replacement part pricing. The technical considerations will remain as they are but repair will probably become less labor-intensive as automation becomes more feasible