Oxidation failure of TBC systems: An assessment of mechanisms

► TBC failure occurs at a critical value of strain energy within the TGO layer only. ► A lower bound value of 55 J.m− 2 is suggested. ► Transformation strains within the bondcoat are not significantly damaging. ► Mechanical instability of the bondcoat is restricted with an adherent topcoat. ► TGO growth induces out-of-plane tensile stresses on non-planar bondcoat surfaces.