Microstructural, Thermo-physical and Mechanical Characterization of a Laser Remelted Plasma Sprayed NiCrAlY/8YSZ Thermal Barrier Coating (TBC) on Inconel 718
P. Kadam, N. Kadam, G. Karthikeyan, D. Kulkarni and A. Damale
Investigations of surface structure, thermo-physical properties and mechanical properties of a thermal barrier coating (TBC) fabricated from NiCrAlY/8YSZ subjected to a laser remelting process have been conducted. The NiCrAlY/8YSZ was deposited onto an Inconel 718 substrate using the atmospheric plasma spay (APS) process. A CO2 laser was then used to remelt the TBC to effect a change in structure. Thereafter, the surface structure, thermal properties, and mechanical properties like hardness and roughness were evaluated. It was found that as-sprayed TBC develops a splat layer structure with few loosely bound particles with the presence of defects. The laser remelting process modifies the TBC surface producing a smooth region with dense hexagonal equiaxed grains. The as-sprayed TBC surface showed defects and loose partially melted particles contributing to a rough area. In contrast, laser remelting improved the TBC surface structure, resulting in a dense grain structure forming a smooth region. Compared to the as-sprayed TBC, the laser remelted TBC surface is reduced by about 10% in thermal conductivity. Laser remelting also improved thermo-physical and mechanical properties of the TBC, providing better thermal insulation to enhance the TBCs lifetime.
Keywords: CO2 laser, Inconel 718, NiCrAlY/8YSZ, thermal barrier coating (TBC), laser remelting, atmospheric plasma spay (APS), microstructure, mechanical properties, thermo-physical properties