Numerical evaluation and analysis of the adhesion phenomena in thermal barrier coating systems through bio-mimicking plasma process
Master of Science in Mechanical Engineering (MSME)
Thermal Barrier Coatings or TBCs when abbreviated are an imperative part of the thermal protection system of expensive equipment and machinery in the automobile and aeronautics industry. They provide protection to expensive alloy materials upto a temperature of 2700° C without expensive metallurgical additions. Unfortunately, the problem of coating adhesion has plagued the TBC field for years, leading to catastrophic failures in critical TBC systems. Efforts to chemically improve bond strength has not been entirely successful, so the only other efficient way to do this would be some kind of mechanical interlocking that occurs at micro/nano scales. This research work deals with the improvement of adhesion in TBC systems by numerical simulation and bench-marking of micro-geometric surface features that has been synthesized or reproduced in laboratory environment through electrochemical operations. For this, several geometries that benefit mechanical interlocking, and consequently improvements in mechanical 'adhesion' in TBCs has been compared. To simulate the mechanical and thermal loading on the micro geometries and to observe their effect, the commercial finite element software COMSOL was used. An analogy was drawn between the biological, Van der Waals dry adhesion mechanism in Gecko feet and that in the top surface of the thermally grown oxide (TGO) layer in TBC whereas the 'mushroom head geometry' in the Gecko feet provides improved adhesion (as much as 10 folds) compared to other geometries (spatular head, spherical head, or plain triangular crevices). An affordable synthesis process, termed “Electrolytic Plasma Processing (EPP)" for recreating this specific geometry, is also proposed and its utility briefly entertained. The work ends with recommendations and suggestions for future works on this topic.
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Hossain, Naser Imran, "Numerical evaluation and analysis of the adhesion phenomena in thermal barrier coating systems through bio-mimicking plasma process" (2013). LSU Master's Theses. 4081.
Wahab, Muhammad A.