“…In addition to these nucleated precipitates, several cavities were generated in the aged blades heterogeneous microstructure after 55,000 EOH at 870°C mixed with aligned γ′ phase as shown in Figure 5(b), provide evidence of the entrance in tertiary creep phase that can provoke buckets failure. Another life-limiting phenomenon mainly observed in aged buckets nickel-based superalloys at 870°C, was the transformation exhibited in Figure 6, of large blocky MC-Carbides rich in (Ti, Ta) found in γ-matrix into coarse brittle Cr rich M 23 C 6 lines network at the grain boundaries of GTD-111 base material [19,20]. On another side, the cold air circulated during service inside the buckets internal channels, had reacted directly with blades base metal and formed an accumulated thick layer of (Al 2 O 3 , TiO, C 2 O 3 , Er 2 O 3 , SiO 2 ) mixed oxides scales (as shown in Figure 7).…”