Fracture Mechanical Modelling of a Plasma Sprayed TBC System

Power-law characteristics of damage and failure of ceramic coating systems under three-point bending

“…It can be found from Table 1 that the damage coefficient c (average 1.38) of the nanostructured thin coatings (Nx) is larger than c (average 1.01) of the conventional thin coatings (Mx), which implies that the damage failure of the nanostructured thin coatings is faster than that of the conventional thin ones. The minimum initial damage is 0.03-0.06 (D 0 /D f in Tables 1-3), which is also in agreement with the previous report [9]. Comparing the damage coefficient c of the thin coatings in Table 1 with that of the conventional thick coatings in Table 2, it can be seen that c (average 1.78) of the conventional thick coatings is larger generally and the initial damage is also larger, which means the damage of the conventional thick coating systems is faster, and verifies the experimental phenomenon of the obvious catastrophic characteristics of the load-displacement curves of the thick coating systems.…”

“…As above indicated, researchers observed the change of the number of cracks or the crack length with strain, time, temperature or cycling number [2][3][4][7][8][9]. For thicker coatings or pre-oxidized systems, interface fracture between the coating and the substrate occurs, and the interface crack evolution was studied in particular for the coating systems under mechanical or thermal loading [7][8][9][10][11]. Recently, Zhou et al studied in detail the damage and fracture of thermal barrier coatings by coupled acoustic emission and digital image correlation techniques [12], and found a similar damage behavior as in the Renusch and Schütze's study [7].…”

“…Trunova et al studies the damage and failure characteristics of thermal barrier coatings by observing interface crack evolution with increasing high temperature oxidation time [8]. Brodin et al studied fatigue damage of thermal barrier coatings by analyzing interface crack length change with increasing thermal cycling number [9].…”

“…It is clear, when ceramic coating/metallic substrate systems are subjected to bending, tension (mechanical load), high temperature oxidation, or thermal shock (thermal load), the microscopic transverse or interface cracks appear in the ceramic coating systems with increasing load or cycling number (for cycling load), i.e., the damage initiates, the number of the transverse cracks saturates and the interface fractures when the load reaches the maximum allowed value or the cycling number reaches the failure critical number [2][3][4][7][8][9]. As above indicated, researchers observed the change of the number of cracks or the crack length with strain, time, temperature or cycling number [2][3][4][7][8][9].…”

Influence of substrate material on the life of atmospheric plasma sprayed thermal barrier coatings

“…The two main sources of stress in the BC/TC interface during thermal cycling are: 1) stress due to the mismatch in CTE which is introduced during cooling and 2) growth stresses from the TGO. The crack growth FE modelling presented here will only include the former of the stress sources as has been done by several researches [11,25,26].…”