Phase evolutions and failure of a long–term utilized Rene 142 brazed vane

Nickel–based super alloys such as Rene 142 are widely used in turbine vanes due to their exceptional high–temperature performance, yet long–term service in extreme environments leads to complex degradation mechanisms that threaten component integrity. This study investigates the microstructural evolution and failure mechanisms of a Rene 142 brazed turbine vane after more than 40,000 operational hours. Through a combination of scanning electron microscopy (scanning electron microscopy), energy–dispersive x–ray spectroscopy (energy dispersive spectroscopy), and thermodynamic simulations (JMatPro), this work elucidates the interplay between phase transformations, elemental segregation, and crack initiation in vane and brazed regions. Key findings reveal that the Rene 142 brazing alloy exhibits reduced γ′ phase stability (30 wt.‐% at 600 °C vs. 70 wt.‐% in Rene 142), preferential segregation of Cr and Ti, and the formation of brittle intermetallic phases and carbides at grain boundaries. These microstructural changes, compounded by oxidation–driven Al depletion and thermal stresses, promote crack nucleation and propagation within the vane. The study further demonstrates that crack growth is accelerated by rafting of γ′ phases, porous oxide–layer formation, and stress concentration at carbide–rich interfaces. These insights advance the understanding of long–term degradation in brazed superalloys and provide actionable recommendations for improving the design and maintenance of turbine components to mitigate premature failure.