Air–cooled turbine vanes made from nickel– and cobalt–base superalloys undergo distortion, cracking, burning, and material degradation in operation. The complex geometry of the parts and the compositional and microstructural heterogeneity of cast alloys impose limitations on the selection of repair methods. Selective chemical stripping of the diffusion coatings; elimination of cracks and restoration of dimensions by joining processes involving both welding and brazing techniques; and formation of coatings by pack cementation are the major processes employed. These processes may give rise to defects that significantly diminish the integrity of the parts.
MST/104
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