Numerical Investigation into the Effect of Splats and Pores on the Thermal Fracture of Air Plasma-Sprayed Thermal Barrier Coatings

Abstract

The effect of splat interfaces on the fracture behavior of air plasma-sprayed thermal barrier coatings (APS-TBC) is analyzed using finite element modeling involving cohesive elements. A multiscale approach is adopted in which the explicitly resolved top coat microstructural features are embedded in a larger domain. Within the computational cell, splat interfaces are modeled as being located on a sinusoidal interface in combination with a random distribution of pores. Parametric studies are conducted for different splat interface waviness, spacing, pore volume fraction and fracture properties of the splat interface. The results are quantified in terms of crack nucleation temperature and total microcrack length. It is found that the amount of cracking in TBCs actually decreases with increased porosity up to a critical volume fraction. In contrast, the presence of splats is always detrimental to the TBC performance. This detrimental effect is reduced for the splat interfaces with high waviness and spacing compared to those with low waviness and spacing. The crack initiation temperature was found to be linearly dependent on the normal fracture properties of the splat interface. Insights derived from the numerical results aid in engineering the microstructure of practical TBC systems for improved resistance against thermal fracture.

Thermal Barrier Coatings: An Insight into Conventional Plasma Spray and Water-Stabilized Plasma Spray

“…In addition, splat interface waviness improves the TBC fracture more than a flat splat interface. The crack length at the flat splat interfaces is more sensitive to the distribution of pores, as simulated in Figure 4 [18].…”

Progress in ceramic materials and structure design toward advanced thermal barrier coatings

“…Krishnasamy et al [135] analyzed the stress state and crack propagation behavior induced by σ t during cooling by using the macro-micro integration model, as shown in Fig. 26.…”

Uncertainty Quantification of the Lifetime of Self-Healing Thermal Barrier Coatings Based on Surrogate Modelling of Thermal Cyclic Fracture and Healing

“…In a two-dimensional setting, the crack area fraction refers to the crack length fraction per unit depth. The relation given in (7) is used after the first healing event occuring at time t à in conjunction with an equivalent crack opening D p ð Þ for each material (p ¼ 0 original material or p ¼ 1 healing material), with…”

“…Finite element simulations have been extensively used to study the influence of self-healing particles and other microstructural parameters on the TBC lifetime [7][8][9][10][11][12][13][14][15][16][17][18]. These numerical simulation techniques can in general capture the experimentally-observed damage process that occurs in metallo-ceramic material systems [19,20].…”