Advanced TBC Systems by Vapor Deposition Using LPPS Thin Film

Abstract

LPPS-Thin Film is a vacuum plasma spray technology recently developed by Sulzer Metco. In comparison to conventional Vacuum Plasma Spraying (VPS) or Low Pressure Plasma Spraying (LPPS), LPPS-Thin Film uses a working pressure below 2 mbar and a high energy plasma gun. This leads to unconventional plasma jet characteristics which can be used to obtain specific and unique coatings. An additional new feature of LPPS-Thin Film is the possibility to deposit a coating not only from liquid splats by melting the feed stock material but also from gas phase by vaporizing the injected material. The coatings produced from vapor phase show similar structures to EB-PVD layers. The coating thickness can vary from only a few microns up to more than 300 μm. The LPPS-Thin Film process fills the gap between conventional PVD/CVD technologies (≤ 1–5 μm) and standard thermal spray processes (≥ 50 μm). However the concept of “Thin-Film” not only refers to the thickness of the coating. In particular the vaporizing of ceramic coating material also enables new layer properties in a domain between thermal spray and EB-PVD. Yttria Stabilized Zirconia (YSZ) can be deposited with a columnar microstructure. Lab investigations show that these coatings have potential for lower thermal conductivity and higher thermal stress tolerance compared to standard EB-PVD layers.