Experience with repair of stationary gas-turbine blades –view of a turbine manufacturer

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Abstract
Repair procedures for stationary gas–turbine blades, both established practices and techniques which have yet to find wide application, are described. Special attention is paid to quality assurance – making sure that repaired parts do not reduce reliability. Of the various repair techniques, only regenerative heat treatment (including hot isostatic pressing, or hipping) and recoating can be performed as standard procedures. Machining (e.g. grinding) changes the geometry of the blade and requires an exact knowledge of design tolerances. Straightening has to be done very carefully and should be followed by a hipping treatment. The greatest number of restrictions apply when fusion and deposition techniques such as brazing, welding, inserting, sintering, and plasma deposition are used. These techniques are used at present only if it is absolutely necessary to restore heavily worn blades. MST/101