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3828 |
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Friday, May 23, 2014, Hall H1 9:40 AM Aviation Industry 3 |
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Study of the residual stress distribution of thermally-sprayed TBCs involving various interfaces and laser drilling |
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Vincent Guipont* / MINES ParisTech, France Guillaume Montay / LASMIS laboratory, Technologic University of Troyes, France C. Guinard/ , Michel Jeandin/ Materials Research Center, Mines ParisTech, France J. Girardot/ , M. Schneider/ , |
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For the aero-engines, combustion chambers with thermal barrier coating (TBC), the performance of the part is improved by laser drilling of highly numerous cooling holes. The coating must be highly adhesive in order to prevent the ceramic spalling when the laser drilling process is implemented. The residual stresses in thermal barrier coatings play an important role on the intrinsic adhesion and on the spalling behaviour during laser drilling. In this work, the study of the residual stress distribution has been achieved throughout the three layers that compound a TBC: zirconia (ZrO2Y2O3 8 wt. %), bond coat (MCrAlY, M =Ni or CoNi) and cobalt based superalloy. For this study, several TBCs with different bond coats have been prepared especially by plasma spray and cold spray and using various post-treatments. From the different bond-coat/top-coat interfaces, residual stresses profiles with 1mm depth have been determined by the incremental-step hole-drilling method involving speckle interferometry. An original method was also developed in order to determine the residual stress gradient before and after laser drilling (normal incidence), around the drilled zone for various interfaces. Observations with optical microscope and SEM have been carried out to measure the depth drilled and the no-deterioration of the material. The results were discussed to analyze the influence of TBCs interfaces on the residual stresses distribution and to investigate the influence of the laser drilling process on the modification of residual stresses around the hole. |