The nondestructive measurement of strain distributions in air plasma sprayed thermal barrier coatings as a function of depth from entire Debye–Scherrer rings

Abstract

The residual strain distribution has been measured as a function of depth in both top coat and bond coat in as-received and heat-treated air plasma sprayed thermal barrier coating samples. High-energy synchrotron X-ray beams were used in transmission to produce full Debye-Scherrer rings whose non-circular aspect ratio gave the in-plane and out-of-plane strains far more efficiently than the sin 2 method. The residual strain in the bond coat is found to be tensile and the strain in the phase of the as-received sample was measured. The residual strains observed in the top coat were generally compressive (increasing towards the interface), with two kinds of nonlinear trend. These was a 'jump' feature near the interface, and in some cases there was another 'jump' feature near the surface. It is shown how these trend differences can be correlated to cracks in the coating.

Characterization of the stress distribution and evolution inside a thermal barrier coating after initial thermal cycles

“…Therefore, the stress near the TBC interface presents an uneven complex stress state with coexisting tension and compression, as shown in Figure 5D. The above results are consistent with the results published by Li et al 63 …”

“…In Figure 4B, the refractive index and stress of the as‐sprayed TBC specimen were 4.7504 ± 0.0262 and −8.3 ± 43.6 MPa, respectively. With the increase in the number of thermal cycles, the refractive index of the TC layer decreased, and the average stress in the TC layer increased continuously until −180.6 ± 56.0 MPa, indicating that the TC layer was in the compressive stress state during the initial thermal cycle, which is consistent with other work 63 . In addition, the stress standard deviation of the TC layer after four thermal cycles (56.0 MPa) was larger than that after two thermal cycles (26.4 MPa), indicating that the local stress concentration in the TBC specimen was strengthened after four thermal cycles.…”

“…Therefore, the stress near the TBC interface presents an uneven complex stress state with coexisting tension and compression, as shown in Figure 5D. The above results are consistent with the results published by Li et al 63 As shown in Figure 19B, the Y element in part of the T' phase in the TBC specimen diffuses and migrates during long-term sintering in the high-temperature range of 600-1150 • C, 71 resulting in the emergence of yttrium-rich and yttrium-poor regions. The nucleation and growth of the T and C phases were induced by yttrium-rich and yttriumpoor regions, respectively.…”

New systematic study approach of green synthesis CdS thin film via Salvia dye

“…The Debye–Scherrer equation is used to compute the crystallite size (D hkl ) using the strongest peak 41 . where D is the mean crystallite size, λ = 1.5408 Å is the X-ray wavelength, θ is the Bragg diffraction angle and β is the full width at half maximum (FWHM) of the diffraction peak, respectively.…”

An in-depth analysis of nucleation and growth mechanism of CdS thin film synthesized by chemical bath deposition (CBD) technique

“…We determined the mean crystalline sizes of different films using the Debye–Scherrer equation based on the strongest peak 45 . Table 2 presents the estimated crystallite sizes with the help of d-spacing.…”