Oxide and TBC spallation in β-NiAl coated systems under mechanical loading

Quantitative Characterization of the Interfacial Damage in EB-PVD Thermal Barrier Coating

“…The spallation process of the EB-PVD TBC can be generally divided into four stages [8,34,38], as shown in Figure 2I microcracks initiate and propagate at the interface under the combined action of stress and strain cycles in the coating, and the growth of TGO; Figure 2II adjacent microcracks gradually coalesce, causing interfacial delamination, i.e., the YSZ and the BC layer debond locally; Figure 2III when the interfacial delamination reaches a certain size, the debonded YSZ which may be accompanied by TGO buckles from the BC under the compressive thermal mismatch stress, which specifically manifests as the occurrence of "blisters" [39], and (IV) as the delamination size or compressive stress further increases, the buckling zone destabilizes and expands, leading to large spallation of the coating, or the brittle fractures of the YSZ due to excessive bending deformation [36,37]. The compressive thermal mismatch stress to which the YSZ and the TGO are subjected gradually increases with the decreasing temperature, which is the main reason that TBC spallation frequently occurs during cooling [40,41]. To obtain conservative results for the engineering design, the buckling of the YSZ is used as an indicator of TBC failure.…”

Aluminium oxide spallation on NiAl coating induced by compression

“…Many tests were performed, and we describe a single, but typical, set of test parameters: the isothermal ageing stage duration is 20 h (leading to an alumina layer about 1 μm thick), and the mechanical spallation tests are performed at room temperature. Other parameters have been tested and carefully detailed elsewhere to establish major features of oxide spallation for the same coating: temperature effect [21], time spent in the ageing period [18] and statistics of spallation events driven by strain [20,22].…”

Investigation on the effective parameters of through-the-width crack propagation in ceramic coatings due to substrate tension using discrete element method

“…3,[5][6][7] Many experimental investigations have been performed in order to clarify the effects of TGO growth, surface roughness between TC and BC as well as mechanical and thermal loadings on damage initiation and propagation in these structures. 1,[8][9][10][11][12][13][14][15][16] Experimental observations point to the complex behavior of damage evolution in ceramic coatings. However, simple loading conditions make opportunities to study damage and failure mechanisms due to each loading modes to find the most effective factor on crack initiation and progression.…”