Efficiency of α-alumina as diffusion barrier between bond coat and bulk material of gas turbine blades

A magnetron sputtered microcrystalline β-NiAl coating for SC superalloys. Part I. Characterization and comparison of isothermal oxidation behavior at 1100°C with a NiCrAlY coating

“…Therefore, diffusion barrier between the coating and the superalloy substrate is needed to suppress the SRZ formation [48]. In our next article, it will be reported that an active diffusion barrier is able to completely prevent the inter-diffusion between the ␤-NiAl coating and Re-bearing SC superalloy substrate at 1100 • C.…”

“…So it will react with aluminum from both the coating and the substrate during service, and forms an alumina/metal/alumina sandwich structure which has both excellent bonding and diffusion barrier ability. The efficiency of ␣-Al 2 O 3 with TiN buffer layer as diffusion barrier between bond coat and bulk material of gas turbine blades was proved by Müller et al [48]. However, ␣-Al 2 O 3 film can only be deposited at temperatures of 1000 • C or higher because of its very high melting temperature.…”

Platinum-Based Alloys and Coatings: Materials for the Future?

“…Conversely, XRD showed that the surface of the Pt-based alloys mainly consisted of α-alumina -the protective oxide coating that also forms naturally at high temperature. Alpha-alumina acts as a diffusion barrier, minimising diffusion of substrate elements to the surface (Rhys-Jones,1989;Müller & Neuschütz, 2003), due to its high thermal stability at high temperatures (Zheng et al, 2006) and low solubility in molten salts (Chen et al, 2003). A crucible test was then conducted at 950°C to increase the corrosion kinetics (Potgieter et al, 2010), as hot corrosion is more damaging at this temperature (Elliot, 1990;Yoshiba, 1993).…”

Integrated Approach for the Development of Advanced, Coated Gas Turbine Blades

“…By applying a thin intermediate Al 2 O 3 layer, interdiffusion between the bond coat and substrate can be completely or almost completely inhibited (see Figures 10,11). [19][20][21][22] The Al 2 O 3 layer should be as thin as possible in order to minimize thermomechanical load from lattice mismatch, but if it is less than about 3 lm thick it may become unstable during high temperature exposure and not block interdiffusion completely. [19] Chemical Vapour Deposition (CVD) of Al 2 O 3 on metallic substrates may lead to whisker growth, [19][20][21]23,24] …”