Service damage mechanism and interface cracking behavior of Ni-based superalloy turbine blades with aluminized coating

•The failure of aluminized turbine blade is mainly induced by the cracking at the interface.•Evident cross-sectional delamination develops on the turbine blade surface after aluminizing.•Interdiffusion zone is formed by the mutual diffusions of Al and alloying elements.•Large amount of directional penetrations of σ phases in the substrate diffusion zone.•Interaction of pores, carbides and σ phases leads to the interfacial cracking of aluminized blades. The service damage mechanism of K403 Ni-based superalloy turbine blade with the aluminized coating are investigated systematically. Fracture morphologies are inspected with a failure event, and the microscopic damage mechanisms are explored based on the aluminized blades with different operation times. It concludes that the formation of massive pores, aggregation of bulk carbides, coarsening and breaking of σ phases, development of continuous γ′ film, etc, lead to the multi-source fatigue cracking at the interface, with the grain boundaries and Kirkendall non-contact areas as the propagation channels, resulting in the rapid fatigue failure and significant life reduction of aluminized turbine blades.