The Isothermal Oxidation Behavior of a Ti3Al-Nb-V-Mo Alloy
The isothermal oxidation behavior of Ti-24Al-14Nb-3V-0.5Mo alloy in synthetic air from 700°C to 1000°C was studied. The main emphasis was focused on the effect of microstructure obtained by different processes of melting and hot rolling, i.e. large and duplex of 2+B2, on the oxidation resistance. Regardless of the microstructure, the overall oxidation process of the specimens exposed at 700°C was dominantly controlled by the beneficial effect of Nb-addition due to the formation of a continuous -Al2O3 layer in the scale. However, both specimens showed poor oxidation resistance above 900°C, especially for the as-rolled specimen, because of higher volume fraction of the 2-phase. The spallation occurred in both specimens at 1000°C, which was probably relative to the formation of Ti2AlN between the thick scale and the substrate except for the TiO2 and -Al2O3.
High-temperature oxidation of hot-dip aluminizing coatings on a Ti3Al–Nb alloy and the effects of element additions
Abstract Hot-dip aluminizing and interdiffusion treatment were used to develop TiAl 3 -rich coatings on a Ti 3 Al–Nb alloy. The addition of Si, Mn, or Ag to the coatings improves the thickness uniformity and reduces the formation of the through-thickness transverse cracks. The element additions promote the formation of dense and continuous Al 2 O 3 -rich scales during the high-temperature oxidation. A layered structure of Al 2 O 3 /TiAl 3 /(TiAl 3  + TiAl 2 )/TiAl/Ti-depleted alloy/alloy from the outside to the inside forms after oxidation at 900 °C without changing the main body of the Si- or Mn-modified coating, and the Ag-modified coating develops a layered structure of Al 2 O 3 /TiAl 3 /(TiAl 3  + TiAl 2 )/(TiAl 2  + TiAl 3 )/TiAl/alloy.
Composite monolayer fabrication by an arc-spray process
A single layer (monotape) technique for fabricating complex high-temperature tungsten-fiber-reinforced superalloy composites is proposed. The fabrication of sheets of arc-sprayed monotape 38 cm wide and 122 cm long has been demonstrated. Composites fabricated using the method are shown to have equal tensile strength and a cleaner matrix than composites fabricated from powder metal cloth monotapes, and the present technique is less expensive than the powder metal fabrication techniques.