Modelling of the interdiffusion and oxidation of a multilayered chromia forming thermal barrier coating

Abstract

The stability of multilayered coatings is important in long-term use and thus accurate predictions of the effects of exposure at temperature are extremely important. In this paper, the prediction and validation of a multilayered thermal barrier coating with a bond coat based on the MCrAlY system is presented. The coating was a three layered bond coat consisting of a NiCrAlY layer with an aluminised outer region onto which a NiCr layer with 2 wt% Si had been deposited. Onto this an yttria partially stabilised zirconia topcoat was applied.The coating system was exposed to 800 8C for times up to 3000 h.The specimens were sectioned and scanning electron micrographs obtained. Energy dispersive spectroscopy, EDS, was used to provide compositional data on each of the layers in the starting condition and also to produce elemental profiles through the sections with increasing time at temperature. The oxidation kinetics were determined from oxide growth measurements over time. The variation of these elemental profiles with exposure time were compared with the ODIN finitedifference code, which also allowed for chromium depletion due to its selective oxidation. Generally, satisfactory agreement was found.

Multilayered Coatings for High-Temperature Steam Oxidation: TGA Studies up to 1000 °C

“…This surface engineering technology, which is also called as ''thermochemical processing,'' diffusion coating process,'' ''pack cementation,'' is based on the CVD principles (Ref [17][18][19][20][21][22][23][24][25][26] and is applicable for industrial large-size products. In addition, it would be reasonable to consider the coatings with more complex architectures (i.e., with more protective layers), since, according to the recent studies (Ref [27][28][29][30][31][32], such composite structures have also high potential in corrosion applications.…”

Environmental protection of Nb/Nb5Si3-based alloys by E/TBC systems

“…At the bond coat/topcoat interface, an adherent protective oxide scale formed composed of a thick outer chromia layer and a thin inner silica layer. The YSZ topcoat did not spall off during exposure to laboratory air at 800°C for up to 3000 h [35]. Promising results were also obtained for YSZ topcoats on a chromia forming NiCr substrate.…”

“…There are only few papers dealing with chromia forming bond coats. These TBC systems consisted of plasma sprayed YSZ on Ni-based superalloys with multilayer bond coats comprising an aluminized NiCrAlY layer and an outer NiCr layer containing also low amounts of silicon [33][34][35]. At the bond coat/topcoat interface, an adherent protective oxide scale formed composed of a thick outer chromia layer and a thin inner silica layer.…”

Mechanism of multi-layer composite coatings in the zinc process of recycling coated WC-Co cemented-carbide scrap

“…The most important ways are dissolution and diffusion. [19][20][21] For a better understanding of the mechanism, the element mapping of the sample in the zinc process was further studied, as shown in Figure 4. It can be seen that Co was distributed in the zinc-enrichment area due to the fact that Zn reacts with Co.…”