A Load-Based Depth-Sensing Indentation Technique for Damage Assessment of Thermal Barrier Coatings

Abstract

In this paper, we present a load-based micro-indentation technique for evaluating material mechanical property as well as degradation evaluation and debonding/spallation detection of thermal barrier coating (TBC) materials. Comparing to the current prevailing nano/micro-indentation methods, which require precise measurements of the indentation depth and load, the proposed technique only measures indentation load and the overall indentation displacement (i.e. including load-induced displacement of the loading apparatus). Coupled with a multiple-partial unloading procedure during the indentation process, this technique results in a load-depth sensing indentation system capable of determining Young’s modulus of metals, superalloys, and single crystal matrices, and stiffness of coated material systems with flat, tubular, or curved architectures. This micro-indentation technique can be viewed as a viable non-destructive evaluation (NDE) technique for determining as-manufactured and process-exposed metal, superalloy, single crystal, and TBC-coated material properties. This technique also shows promise for the development of a portable instrument for on-line, in-situ NDE and mechanical properties measurement of structural components.