Development of New TBC Coating System by Water Plasma Spraying and HVOF

Abstract

A new Thermal Barrier Coating (TBC) system aiming superior thermal shock resistance and low cost, was developed upon combination of HVOF (JP-5000) sprayed CoNiCrAlY bond coating and Water Plasma Sprayed (WPS) yttria-stabilized zirconia top coating for application to industrial gas turbines. This TBC system was evaluated by thermal cyclic test. The new coating system of WPS/JP-5000 showed excellent thermal shock resistance compared to conventional APS (air plasma-spraying)-TBC system against thermal cyclic test condition of 1, 000°C-RT in air. Also the new coating method was confirmed to have good thermal shock resistance even for thick zirconia top coating layer. The superior thermal shock resistance of WPS/JP-5000 coating system was due to formation of microcrack in the top coating layer by WPS. In addition, the CoNiCrAlY bond coating by JP-5000 had a diffusion zone in between the sprayed particles and the substrate similar to VPS coating layers. The new TBC system of WPS/JP-5000 for application to industrial gas turbines is considered promising because its good thermal shock resistance and low cost.