Investigations on the Deposition and the Efficiency of a Multilayer High Temperature Coating System for Gas Turbine Blades

Investigating efficiency of α-Al2O3 diffusion barrier layer in oxidation of EB-PVD NiCrAlY coatings

“…In other words, chromium content was high at the beginning and reduced with the movement toward the depth of coating. In fact, as the aluminium of coating was decreasing toward the TGO layer, β→γ′→γ transformation was happening and, because gamma phase has higher solubility for chromium (Cr solubility limit of gamma phase is higher than 40 wt-% at 1100°C), 17 this region acted as a chromium solvent and, consequently, chromium concentration became higher in this region. Such variations at the interface were observed for chromium and aluminium.…”

“…12,13 Thus, it is essential to create a diffusion barrier in the coating/substrate interface, which prevents or postpones the diffusion of harmful elements and consequently increases the lifetime of coatings. Although various barrier layers such as Al-O-N, 14 dispersed oxide 15,16 and chemical vapour deposition (CVD) a-Al 2 O 3 [17][18][19] have been studied by researchers, few studies have reported the formation and use of electron beam physical vapour deposition (EB-PVD) a-Al 2 O 3 thin layer as a diffusion barrier. In this regard, a-Al 2 O 3 has a hexagonal closed pack structure and is stable at all temperatures up to the melting point.…”

“…In addition, unlike CVD method and the related problems during deposition such as the formation of whiskers, its formation using EB-PVD method is much easier. [17][18][19] In this research, some layers that are made of a-Al 2 O 3 material with different thicknesses were made using EB-PVD method, and their barrier efficiency during isothermal oxidation was investigated and analysed.…”

A review of mechanical and tribological properties of Ni3Al-based coatings-synthesis and high-temperature behavior

“…Since then Silicon based coatings or silicon doped coatings has been well studied and recognized for these applications due to its high temperature oxidation and corrosion resistance properties [62]. Along with these applications, In order to withstand the high temperature in application areas like, gas turbines, jet engines, aerospace industries, nuclear industries and high temperature structural applications for oxidation and corrosion resistance properties (as shown in figure 2), researchers have tried to investigate the properties of Ti and Ni based superalloys coatings [63,64].…”

Investigation of CVD Processes to Perform Dense α-Alumina Coating on Superalloys

“…6,7 Indeed, the upper limit temperature of these coatings is related to the ability of the metallic elements of the diffusion barrier itself to diffuse, or to the crystallization effects of the ceramic layers leading to a drastic microstructural damage. Consequently, further investigations focus on the use of the thermally stable ␣-Al 2 O 3 as a diffusion barrier, 8,9 which is, however, still lacking a satisfactory microstructure and adherence on nickel-based superalloys.…”