Development of nondestructive evaluation methods for structural ceramics

Abstract

Development of nondestructive evaluation (NDE) methods for application to fossil energy systems continues in three areas: (a) mapping axial and radial density gradients in hot-gas filters, (b) characterization of the quality of continuous-fiber ceramic matrix composite (CFCC) joints and (c) characterization and detection of defects in thermal-barrier coatings. In our work, X-ray computed tomographic imaging was further developed and used to map variations in the axial and radial density of two full-length (2.3-m) hot-gas filters. The two filters differed in through-wall density because of the thickness of the coating on the continuous fibers. Differences in axial and through-wall density were clearly detected. Through-transmission infrared imaging with a highly sensitivity focal-plane array camera was used to assess joint quality in two sets of SiC/SiC CFCC joints. High-frame-rate data-capture suggests that our infrared imaging method holds potential for the characterization of CFCC joints. Work to develop NDE methods that can be used to evaluate electron-beam physical-vapordeposited coatings with platinum-aluminide (Pt-A1) bonds was undertaken. Coatings of Zirconia with thicknesses of 125 pm (0.005 in.), 190 pm (0.0075 in.), and 254 pm (0.010 in.) with a Pt-A1 bond coat on RenC N5 Ni-based superalloy were studied by infrared imaging. Currently, it appears that thickness variation, as well as thermal properties, can be assessed by infrared technology.

Comprehensive damage evaluation of localized spallation of thermal barrier coatings

“…Figure 1(a) shows a TBC with partial spallation in its top-coat [32]. The experimental TBC sample is often cylinder plate like and its structure consists of three layers-a substrate, a bond-coat, and a ceramic top-coat.…”

Recent developments in X-ray diffraction/scattering computed tomography for materials science

“…Through the 1980s and 1990s, the use of XR-CT expanded into broader research communities. Initially adopted by clinically adjacent biomedical research communities [11], it was soon espoused by the physical sciences as a non-destructive testing (NDT) method for ceramics and engineering components [12][13][14]. This period also saw the first significant reductions in voxel size (i.e.…”

Nondestructive Evaluation of Thermal Barrier Coating Systems Using Ultrasonic Techniques

“…There are a number of existing test methods used to inspect TBC systems such as Mid-infrared reflectance (MIR) imaging, X-ray diffraction, and Infrared (Eldridge et al 2005;Ellingson et al, 1997;Muralidhar et al, 2006). These techniques are effective in evaluating the defects and material properties within, however the techniques generally required sophisticated machinery setup, huge cost with poor flexibility to perform on-site job.…”

“…However, the complex nature of TBC system has attenuation, porosity, microcracks and is composed of different materials, and these characteristics create difficulties that would need to be overcome to develop a suitable NDE method (Ellingson, et al, 1997). An effective NDE method can be used to monitor the TBC system performance and provide a continuous remaining lifetime prediction.…”