Laser texturing at interface for improved strain tolerance and thermal insulation performance of thermal barrier coatings

Abstract

Titanium alloys have become indispensable materials for lightweight and high-thrust-to-weight-ratio aeroengines owing to their low densities and high specific strengths. However, as the thrust-to-weight ratio increases, the temperature in an aeroengine increases to values considerably above the service temperature of the titanium alloy. Effective design and preparation of the interface structure are a potential approach to enhance the service life and dependability of thermal barrier coatings (TBCs). In this study, TBCs were prepared by spark plasma sintering (SPS) on Ti-6Al-4V, and a texture was engraved at the bond coating (BC)/top coating (TC) interface by a fibre laser. The laser texturing induced segmentation cracks. High-density segmentation cracks (dense vertical cracks (DVCs)) could be formed at densely spaced areas of the texturing. Based on the bimodal structure characteristic obtained by SPS, bimodal-structured DVC TBCs were realised, which provided the coating with higher strain tolerance and thermal insulation performance. After 138 cycles of thermal shock at 800 °C, the spallation area of a 2-mm square coating was only 34.55 % of that of unengraved TBCs. In addition, the laser-textured coating had a better thermal insulation performance. The thermal insulation temperature of a hexagonal 2-mm coating reached 215 °C.