Assessment of the degraded high-pressure blades in a land-based gas turbine

Abstract

The purpose of this paper is to evaluate high-pressure turbine blades after a long-term thermal exposure in a land-based gas turbine. Emphasis is placed upon structure and composition of the various layers evolving, on the one hand, due to hot oxidation/corrosion attacks and, on the other hand, because of interdiffusion phenomena between the substrates and their protective coatings. This work therefore discusses the influence of γ′-Ni3 (Al, Ti) precipitates coarsening, needle σ-phase nucleation, and M23C6-Carbides formation on the hardness properties of blades. In addition, this assessment attempts to evaluate the influence of γ′-Ni3 (Al, Ti) orientation changes and crystallites size growth on the intrinsic degradation of GTD-111 and IN738LC substrates