Erosion Failure Mechanism and Model Establishment of Thermal Barrier Coatings Based on Roughness

doi:10.3724/SP.J.1077.2014.13342

Abstract

Abstract:

Erosion failure mechanism of atmospheric plasma sprayed (APS) ZrO₂-7%Y₂O₃(7YSZ) thermal barrier coatings (TBCs) was studied with a san-blasting erosion tester. The failure features of TBCs with laminar and porous structure were investigated using impingement angle 90° at room temperature. Effect of porous and laminar structure on erosion rate was analyzed. Moreover, regarding the failure factors, the relation of ceramic coating roughness and erosion rate was analyzed and their mathematic model was established. The experimental results indicate that the factors of porous and laminar structures play an important role in crack propagation in TBCs. For the TBCs with ununiform, discontinuous pressure-pressure pulsating cyclic load under impact of high velocity particles, the ceramic coatings are loaded with normal stress and shear stress, in which the normal stress leads to appearance of pit in ceramic coating and the shear stress leads to grooves. Meanwhile, the crack propagation in grain boundaries and interfaces of laminar structure will appear based on the net cracks on ceramic coating surface in sprayed TBCs, which will lead to particle exfoliation and flaky debris. So the erosion failures of TBCs follows abrasive wear and low cycle fatigue mode. The relevance between ceramic coating roughness and erosion rate indicates an increased linear relation.

Key words: thermal barrier coating, erosion mechanism, roughness

CLC Number:

TQ174

ZHANG Xiao-Feng, ZHOU Ke-Song, ZHANG Ji-Fu, HAN Tao, Song Jin-Bing, LIU-Min. Erosion Failure Mechanism and Model Establishment of Thermal Barrier Coatings Based on Roughness[J]. Journal of Inorganic Materials, 2014, 29(3): 294-300.

Figures/Tables 9

Fig. 1 SEM images of NiCoCrAlYTa powders (a) and 7YSZ powders (b)

Fig. 2 Schematic diagram of san-blasting erosion tester

Fig. 3 3D topologies of ceramic coating with different roughnesses

Fig. 4 Relationship between erosion rate and time for ceramic coating with different roughnesses

Fig. 5 Relation between erosion rate (ER) and roughness (Ra) for ceramic coating

Fig. 6 Different magnification surface microstructures of ceramic coating Protection district, (a1, a2); Erosion district after erosion for 120 s, (b1, b2, b3)

Fig. 7 Cross-sectional microstructures of protection district and erosion district Whole district (a), protection district (b), erosion district (c-f) after erosion for 120 s

Fig. 8 Sand-blasting erosion failure model under 90°

Fig. 9 Erosion schematics of ceramic coating with different roughnesses

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