| Title |
Study on Laser Surface Modification of NiCrAlY / 8wt%Y2O3-ZrO2 Two-Layer Thermal Barrier Coating (TBC) Fabricated by Plasma Spray Method |
| Authors |
이선호(Seon Ho Lee) ; 유재성(Jae Seong Yoo) ; 김종영(Jong Young Kim) ; 강춘식(Choon Sik Kang) |
| Abstract |
NiCrAlY/8wt%Y₂O₃-ZrO₂, two layer TBC was fabricated by plasma spray method and its surface modification was performed by CO₂ laser and then the change of characteristics and failure mechanism during thermal shock test were investigated. The more specific energy of laser beam, the more crack width and thickness of melted layer originated by laser treatment. In the same specific energy, they decreased by reducing laser power. After laser treatment, residual stress was altered tensile stress, adhesion strength reduced due to the horizontal crack at the bottom of interface between melted and unmelted layer, surface corrosion of ceramic layer was suppressed due to densification and the life cycle by thermal shock test were increased. The failure procedure during the thermal shock test was as follows; buckling occurred first, then spalling followed after a few cycles and fracture region was expanded. The failure resulted from buckling is believed to occur because of compressive stress developed by cooling. It is thought that thermal shock lifetime after laser treatment is improved owing to the stress relaxation caused by vertical crack to surface and residual tensile stress. |