What are the disadvantages of Inconel 718?
Inconel 718 is a high-performance Nickel-Ferrous-Chromium based superalloy originally developed by Eiselstein of International Nickel Company in late 1950s for gas turbine engine. It is giving a major contribution to comply with the requirements of advanced gas turbine engines.
It is extensively employed in the aerospace sector due to its good weldability and exceptional mechanical properties than other grades of superalloys. The high thermal strength in Inconel 718 alloy is predominantly achieved by the precipitation of γ prime - [Ni3Ti, Ni3Al)] and γ double prime - [Ni3Nb] phases. General Electric Company expends 34% of Inconel 718 alloy in CF6 engine of Boeing-787 for the fabrication of aeroengine components. It is used in the hot sections of rockets and gas turbines such as for blades, discs and casings of the high-pressure region of compressor and discs as well as some blades of the turbine section where high temperature strength, exceptional creep and stress rupture properties, good resistance to hot corrosion and oxidation are major requirements. It involves two strengthening modes: solid solution strengthening (atoms of Fe, Cr, Mo and Nb substitute Ni within Ni matrix) and precipitation hardening by γ′ and γ″ precipitates. At a temperature near to 650 °C, Nb combines with Ni to form γ″ phase (Ni3Nb) which provides excellent mechanical properties at very high temperatures.
