Interfacial fracture characteristic and crack propagation of thermal barrier coatings under tensile conditions at elevated temperatures

Abstract

Thermal barrier coatings (TBCs) have been extensively used in aircraft engines for improved durability and performance for more than fifteen years. In this paper, thermal barrier coating system with plasma sprayed zirconia bonded by a MCrAlY layer to SUS304 stainless steel substrate was performed under tensile tests at 1000 • C. The crack nucleation, propagation behavior of the ceramic coatings in as received and oxidized conditions were observed by high-performance camera and discussed in detail. The relationship of the transverse crack numbers in the ceramic coating and tensile strain was recorded and used to describe crack propagation mechanism of thermal barrier coatings. It was found that the fracture/spallation locations of air plasma sprayed (APS) thermal barrier coating system mainly located within the ceramic coating close to the bond coat interface by scanning electron microscope (SEM) and energy dispersive X-Ray (EDX). The energy release rate and interface fracture toughness of APS TBCs system were evaluated by the aid of Suo-Hutchinson model. The calculations revealed that the energy release rate and fracture toughness ranged, respectively, from 22.15 J m −2 to 37.8 J m −2 and from 0.9 MPa m 1/2 to 1.5 MPa m 1/2 . The results agree well with other experimental results.

Behaviour of alumina-coated 304L steel in a Waste-to-Energy plant

“…As far as the bonding between the two materials was good (resistance in traction above 70 MPa at room temperature [26]), and considering that the tensile strength of alumina (with a porosity N 10%) does not exceed 172 MPa at 298 K and decreases when temperature increases [33], the coating cracked most likely a few minutes after the introduction of the samples in the furnace. The direction of the cracks (perpendicular to the surface of the substrate) is consistent with this mechanism [34,35].…”

Acoustic emission analysis on tensile failure of air plasma-sprayed thermal barrier coatings

“…9 then deflect into interface cracking or delamination with the increase of tensile stress [30,31] . Therefore, the characteristic frequency spectrums and corresponding dominant bands of an AE signal can be obtained after a series of the FFT analysis.…”

Thickness-dependent fracture characteristics of ceramic coatings bonded on the alloy substrates

“…Once the ceramic coatings flaked off and the interfaces between the coatings and the metallic substrates fractured, the substrates exposed in high temperature environment would fail. The fracture characteristics of the coating systems have been studied by the uni-axial tension tests [3][4][5][6], and the interface fracture toughness was analyzed based on the Suo-Hutchinson model [7]. For example, Zhou et al studied different fracture modes of the functionally grade material coatings and the non-functionally grade material coatings [3].…”