Abstract
To obtain appropriate crucible materials for vacuum induction melting of MCrAlY alloys, four different oxide ceramics, including MgO, Y2O3, Al2O3, and ZrO2, with various microstructures were designed and characterized. The high-temperature wettability and interactions between Ni-20Co-20Cr-10Al-1.5Y alloys and oxide ceramics were studied by sessile drop experiments under vacuum. The results showed that all the systems exhibited non-wetting behavior. The contact angles were stable during the melting process of alloys and the equilibrium contact angles were 140° (MgO), 148° (Y2O3), 154° (Al2O3), and 157° (ZrO2), respectively. The interfacial reaction between the ceramic substrates and alloys occurred at high temperature. Though the ceramics had different microstructures, similar continuous Y2O3 reaction layer with thicknesses of about 25 μm at the alloy-ceramic interface in MgO, Al2O3, and ZrO2 systems formed. The average area percentage of oxides in the alloy matrices were 0.59% (MgO), 0.11% (Al2O3), 0.09% (ZrO2), and 0.02% (Y2O3), respectively. The alloys, after reacting with MgO ceramic, had the highest inclusion content, while those with the lowest content were in the Y2O3 system. Y2O3 ceramic was the most beneficial for vacuum induction melting of high-purity Y-containing Ni-based alloys.
Highlights
With the development of the aviation industry, the inlet temperature of military large-scale engine turbines has been increased to 1850–2000 K
MCrAlY (M = Ni and/or Co) alloys are widely used as overlays or bond coats for thermal barrier coatings (TBCs) to protect gas turbine blades and other hot components against high-temperature oxidation and hot corrosion [3,4]
vacuum induction melting (VIM) is the only vacuum melting method that uses a refractory crucible made of oxides such as SiO2, CaO, Al2 O3, ZrO2, and MgO [7,8]
Summary
With the development of the aviation industry, the inlet temperature of military large-scale engine turbines has been increased to 1850–2000 K. The working temperature of hot-end components of aero-engines is getting higher and higher, and is affected by the oxidation and corrosion of high-temperature gas [1,2]. MCrAlY (M = Ni and/or Co) alloys are widely used as overlays or bond coats for thermal barrier coatings (TBCs) to protect gas turbine blades and other hot components against high-temperature oxidation and hot corrosion [3,4]. VIM has been almost the most common method for nickel-based superalloys. VIM is the only vacuum melting method that uses a refractory crucible made of oxides such as SiO2 , CaO, Al2 O3 , ZrO2 , and MgO [7,8]. The refractory is a contamination source of oxygen because the metal/refractory interface has a thermal mechanical
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