Effect of Laser Treatment on the Surface Roughness of Multilayer Plasma Sprayed Thermal Barrier Coating System

Abstract

Thermal barrier coatings (TBCs) are used in advanced engines working athigher temperatures. Higher efficiency and performance of gas turbineengines will require careful selection of TBCs. In this study,Ni22Cr10Al1.0Y (Amdry 9625) bond coat and two types of top coatincluding ceria stabilized zirconia (CSZ) ZrO2-24CeO2-2.5Y2O3) and yttriastabilized zirconia (YSZ) ZrO2-8Y2O3 were deposited on IN 625 by airplasma spraying (APS). The thickness of the duplex ceramic coat based onzirconia was in the range between 350 to 400 µm. The effect of highpower Yb:YAG solid state laser at different laser parameters on feature,microstructure and roughness of plasma sprayed and laser sealed coatingof multilayer ceria stabilized zirconia/ yttria stabilized zirconia wasinvestigated. Surface roughness has been reduced significantly after lasersealing. The effect of laser process parameters carried out using Taguchi’sL16 orthogonal array design. Minimum roughness can be obtained atmoderate power density and longer interaction time with sufficient specificenergy to produce complete melting of coating. Characterization andanalysis of results was achieved by employing scanning electronmicroscopy (SEM) , (EDS) and image J analysis. It was found from theresults, there were significant improvements in the performance of plasmasprayed coatings after laser sealing due to the reduction of surface coatingdefects