Quantitative Evaluation of Partial Delamination in Thermal Barrier Coatings Using Ultrasonic C-scan Imaging

• Published in: International journal of precision engineering and manufacturing Vol. 21; no. 1; pp. 157 - 165
• Main Authors: Kishore, M. B., Lee, Ho-Girl, Abera, A. Gezaei, Kim, H. J., Seok, C. S., Song, S. J.
• Format: Journal Article
• Language: English
• Published: Seoul Korean Society for Precision Engineering 2020; Springer Nature B.V
• Subjects: Base metal; Coatings; Computer simulation; Delamination; Engineering; Industrial and Production Engineering; Materials Science; Metal surfaces; Quantitative analysis; Review Paper; Signal processing; Sound waves; Thermal barrier coatings; Thermal imaging; Thermodynamic efficiency; Turbine engines; Ultrasonic testing; Thermally grown oxide; Thermal aging; Delamination; Thermal barrier coating; Ultrasonic C scan
• ISSN: 2234-7593; 2005-4602
• DOI: 10.1007/s12541-019-00143-8

Adoption of thermal barrier coatings (TBC) will help to improve the durability and thermal efficiency of turbine engines. Delamination of TBC owing to thermally grown metal oxides is a critical issue that needs periodical evaluation to ensure safety and effective maintenance for the financial benefits of industry. In this paper, a methodical approach using ultrasonic C-scan technique for quantitative evaluation of partial delamination area in TBC specimens was investigated. Preliminary studies were conducted using acoustic simulations and the experiments were carried out on a set of coin shaped TBC specimens prepared using plasma spray technique and isothermally degraded at 1100 °C for 25 h, 50 h, 100 h, and 150 h. Ultrasonic C-scans were performed using pulse echo technique with incident ultra sound radiation inclined normal to the surface of base metal of TBC system. Delamination maps of respective specimens were formulated from ultrasonic signals through proper signal processing and analysis techniques and the degree of delamination was evaluated with the help of existed mathematical model. The simulation results shows good agreement with the experimental data and this approach shows ability to estimate the degree of delamination from base metal surface.