Multilayer GZ/YSZ Thermal Barrier Coating from Suspension and Solution Precursor Plasma Spray

TL;DR

This paper presents a novel multilayer thermal barrier coating combining GZ and YSZ layers produced by plasma spray techniques, enhancing resistance to high-temperature degradation and CMAS attack in gas turbines.

Contribution

Introduces a new multilayer TBC fabrication method using suspension and solution precursor plasma spray to improve high-temperature stability and CMAS resistance.

Findings

Triple-layer coating shows superior CMAS resistance.

Both coatings perform similarly in furnace and burner rig tests.

GZ and YSZ multilayers enhance thermal barrier performance.

Abstract

Gas turbines rely on thermal barrier coating (TBC) to thermally insulate the nickel-based superalloys underneath during operation; however, current TBCs, yttria stabilised zirconia (YSZ), limit the operating temperature and hence efficiency. At an operating temperature above 1200{\deg}C, YSZ is susceptible to failure due to phase instabilities and CMAS (Calcia-Magnesia-Alumina-Silica) attack. Gadolinium zirconates (GZ) could overcome the drawback of YSZ, complementing each other with the multi-layer approach. This study introduces a novel approach utilising axial suspension plasma spray (ASPS) and axial solution precursor plasma spray (ASPPS) to produce a double-layer and a triple-layer TBCs with improved CMAS resistance. The former comprised suspension plasma sprayed GZ and YSZ layers while the latter had an additional dense layer deposited through a solution precursor to minimise the columnar gaps that pre-existed in the SPS GZ layer, thus resisting CMAS infiltration. Both coatings performed similarly in furnace cycling test (FCT) and burner rig testing (BRT). In the CMAS test, triple-layer coating showed better CMAS resistivity, as evidenced by the limited CMAS infiltration observed on the surface.