Nondestructive Determination of Thickness and Elastic Modulus of Plasma Spray Coatings Using Laser Ultrasonics

Abstract

<p>Plasma sprayed coatings are widely used to protect parts from aggressive environments. In applications such as land-based gas turbines, Thermal barrier Coatings (TBCs) are utilized to protect the turbine components from very high operating or firing temperatures [1]. The TBCs are commonly applied by standard air plasma spray process, which is an open-loop operation with no feedback about the coating conditions during deposition. Unfortunately, on-line variations of the spray conditions, such as the continuous wearing of the torch hardware, can adversely affect the coating quality and create significant part-to-part variations. The standard method of evaluating coatings is destructive in nature; hence these tests cannot be performed on each produced part [2]. As a result, coated parts may not have the consistent quality and durability needed for many applications [3].</p>