This study evaluates the thermal and mechanical properties of plasma-sprayed lanthanum zirconate thermal barrier coatings and compares them with conventional 8YSZ TBCs. The La 2 Zr 2 O 7 coatings were found to have a lower thermal conductivity than 8YSZ, although this is offset by lower bond cap tensile strength and poor erosion resistance. A double-layered structure with a La 2 Zr 2 O 7 coating on porous YSZ was also tested and is shown to have better thermal shock performance than single-layer La 2 Zr 2 O 7 and double-layer structures formed on dense 8YSZ sublayers.

This work investigates the effect of calcium-magnesium aluminosilicate (CMAS) deposits on thermal barrier coatings. CMAS infiltration was achieved by means of a cement tape containing synthetic glass powder. The tape was placed on coating surfaces and melted in a tube furnace or with a flame burner. The resulting coating failures were investigated by examining thermomechanical and thermochemical interactions between the coatings and aluminosilicate deposits. It was found that the porous nature of thermal spray TBCs makes them vulnerable to CMAS attack even before discernible chemical reactions start. Possible mitigation approaches are proposed for improving coating life under such conditions.

The most advanced thermal barrier coating (TBC) systems for aircraft engine and power generation hot section components consist of EBPVD applied yttria stabilized zirconia and platinum modified diffusion aluminide bond coating. Thermally-sprayed ceramic and MCrAlY bond coatings, however, are still used extensively for combustors and power generation blades and vanes. This paper highlights the key features of plasma spray and HVOF, diffusion aluminizing and EBPVD coating processes. The coating characteristics of thermally sprayed MCrAlY bondcoat as well as low density and dense vertically cracked (DVC) Zircoat TBC are described. Essential features of a typical EBPVD TBC coating system, consisting of a diffusion aluminide and a columnar TBC, are also presented. The major coating cost elements such as material, equipment and processing are explained for the different technologies, with a performance and cost comparison given for selected examples.

The Cold Spray coatings have been sprayed from binary eutectic alloy – Al-12%Si and from the complex composition iron-based alloy. The atomized Al-Si powder had close to microcrystalline (grain size around 1micron) structure, the Fe alloy powder had amorphous-nanocrystalline structure. Aluminum-based alloy was also sprayed with addition of up to 10% of aluminum oxide powder. The coating structure and properties have been investigated using optical microscopy, scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, microcalorimetry, microhadness, tensile, bend, erosion and abrasion tests, and corrosion polarization tests. It has been shown that the Al-Si coatings have microcrystalline structure, and the Fe-based coating have amorphous-nanocrystalline structure similar but not identical to the feedstock powders. Cold Spray process has a specific mechanism to preserve the powders metastable structures. The coatings have enhanced hardness, wear and corrosion resistance. Abstract only; no full-text paper available.