Tensile fracture behavior of thermal barrier coatings on superalloy

Tensile fracture behavior of thermal barrier coatings (TBCs) on superalloy was investigated in air at room temperature (RT), 650 °C and 850 °C. The bond coat NiCrAlY was fabricated by either high velocity oxygen fuel (HVOF) or air plasma spraying (APS), and the top coat 7%Y2O3–ZrO2 was deposited by APS. Thus two kinds of the TBC system were formed. It was shown that the coating had little effect on tensile stress–strain curves of the substrate and similar tensile strength was obtained in two kinds of the TBC system. However, the cracking behavior in the two kinds of TBC system at RT was different, which was also different from that at 650 °C and 850 °C by scanning electron microscopy. The interface fracture toughness of the two kinds of TBC system was evaluated by the Suo–Hutchinson model and the stress distribution in the coating and substrate was analyzed by the shear lag model.

Research Highlights
► The coating had little effect on tensile stress–strain curves of the substrate.
► The specimen symmetry influences cracking modes at room temperature.
► The nature of the coating decides failure behaviors of the coated system.