Investigation of the Interface Diffusion Layer’s Impact on the Thermal Cycle Life of PS-PVD Thermal Barrier Coatings

Abstract

The behaviour of the interdiffusion layer between the ceramic layer and the metal bonding layer in thermal barrier coatings, resulting from high-energy beam coating deposition, is a critical factor influencing the thermal cycle life of these coatings. Given that the interdiffusion layer at the interface of plasma spray-physical vapour deposition (PS-PVD) coatings has been relatively underexplored and its influencing mechanisms remain unclear, this study investigates how different pre-oxidation layer states affect the thermal cycle life of PS-PVD coatings. Under conditions conducive to effective pre-oxidation film formation and minimal interdiffusion between NiCrAlYSi and 8YSZ, we observed an increase in thermal cycle life from 1000 h at 1100 °C to 2150 h. The application of high-heat flux jets, along with coupling factors related to preheating and pre-oxidation processes, can modulate interdiffusion at the interface. A thinner interdiffusion layer not only reduces oxidation rates but also enhances the longevity of the coating’s thermal cycle. Ultimately, cracks may develop within the composite oxide film, leading to coating failure. The Al-rich component present in both the interdiffusion composite oxide diffusion layer and initially deposited gas phase 8YSZ contributes to a reduction in TGO growth rate, as well as interface stress levels. In scenarios involving high-heat flux jet preheating coupled with coating deposition processes, the oxygen ion concentration emerges as a pivotal factor regulating interdiffusion dynamics. This research holds significant implications for elucidating the formation mechanisms underlying interdiffusion layers while simultaneously enhancing PS-PVD coating lifespans.