Influence of laser shaping of the topography of NiCrAlY sinters on the surface oxidation mechanism under high-temperature conditions

This work presents the idea of functionalization of bond coat surface in thermal barrier coatings technology. The laser surface shaping not only topographically alters the surface but also affects the interfacial behaviors in multilayer coating systems, significantly impacting e.g. high-temperature oxidation mechanisms.

In this study, NiCrAlY powder was sintered and then laser microtextured. The free-standing sinters with six various topographies were then exposed to isothermal oxidation at 1100 °C and the dwell-time in range of 1 to 168 h. The further microstructural studies were aimed at exploring the correlation between microtexturing parameters, the resulting topography, and high-temperature oxidation mechanisms. The topographical evolution of the laser-treated sinters was analyzed using a scanning electron microscopy and confocal microscopy. Additionally, high-resolution electron microscopy coupled with in-situ focused ion beam etching and energy-dispersive spectroscopy, as well as electron backscatter diffraction were utilized to examine the migration of chemical elements and the final composition of thermally grown oxides, while x-ray diffraction was used to investigate surface oxide formations. The observations revealed that laser surface processing results in fine subsurface microstructure related to rapid free-cooling. Microstructural changes further affected the high-temperature behavior of NiCrAlY powder by altering the oxidation kinetics and oxide formation during isothermal oxidation.