Damage evolution in a self‐healing air plasma sprayed thermal barrier coating containing self‐shielding MoSi₂ particles

Abstract

A self-healing thermal barrier coating (TBC) system is manufactured by air plasma spraying (APS) and tested by thermal cycling. The ceramic topcoat in the self-healing APS TBC system consists of an yttria stabilised zirconia (YSZ) matrix and contains self-shielding aluminium containing MoSi 2 healing particles dispersed close to the topcoat/bond coat interface. After spraying the healing particles the material was annealed to promote the formation of an oxygen impermeable Al 2 O 3 shell at the MoSi 2 -TBC interfaces by selective oxidation of the aluminium fraction. The samples were subsequently thermally cycled between room temperature and 1100°C. The study focussed on the spontaneous formation of the Al 2 O 3 shell as well as the subsequent damage evolution in the APS produced TBC during thermal cycling. Experimental evidence showing characteristic signs of crack healing in the topcoat is identified and analysed. The study shows that while the concept of the self-healing APS TBCs containing self-shielding MoSi 2 particles is promising, future study is needed to improve the protectiveness of the Al 2 O 3 shells by further tailoring the aluminium content in the MoSi 2 and the particle shape to avoid the premature oxidation of the healing particles and maximise crack healing efficiency. K E Y W O R D SAl-containing MoSi 2 ,

Determination of fracture toughness of a platinum-modified nickel aluminide coating by micromechanical testing

“…The STEM samples were in the form of thin lamellae prepared by FIB milling through the cross-section of the coating. More details about the STEM sample preparation procedure could be found elsewhere [39][40][41].…”

Crack-Resistance Behavior of an Encapsulated, Healing Agent Embedded Buffer Layer on Self-Healing Thermal Barrier Coatings

“…The continuous growth of TGO and some spinel Figure 8 shows the cross-sectional microstructure around the delaminated area after CTF tests. During thermal cycling, different thermo-mechanical properties between the matrix and healing agent could develop stress, so only 10 vol% of healing agents was blended with YSZ to minimize the development of stress, which was founded in other previous studies [27,29]. extrinsic toughening mechanism [41].…”

“…Furthermore, the healing agents were encapsulated by a sol-gel method to prevent their loss during coating fabrication, showing enhancement of oxidation resistance [28]. Chen et al [29] developed self-shielding healing particles, which produced an oxygen impermeable Al 2 O 3 shell, and identified crack-healing behavior during thermal cycling tests. Ouyang et al [30] introduced a SiC-based healing layer on the surface of the top coat, and showed the filling of the surface cracks and improved oxidation and spallation resistance.…”

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

“…As a result, the TBC lifetime is measured by the number of thermal cycles that the TBC can sustain until spallation. In order to arrest the cracks and potentially improve the TBC lifetime, researchers have investigated the implementation of self-healing particles within the coatings [3][4][5][6]. One of the most widely studied methods of incorporating self-healing properties in a TBC is to include encapsulated healing agents within the top coat, which is the location where cracks typically appear in TBCs (see Fig.…”