Thermodynamic cycles using CO2 in supercritical conditions (sCO2) can provide many advantages for future power generation applications. Thanks to the high fluid density, sCO2 causes a significant machinery size reduction, along with the possibility to achieve very good efficiencies. Due to thermal stability and non-flammability of sCO2, direct heat exchange from a wide range of thermal sources is possible from relatively low to very high temperatures. This makes sCO2 suitable for micro-channel-based heat exchanger technology in close-loop systems in combination with thermal solar power (CSP), biomass, flaring, nuclear and even geothermal sources. However, with sCO2material selection and design problems can raise, since materials must have resistance to high-temperature oxidation, corrosion and deformation under constant mechanical loading (creep resistance), so nickel-based superalloys for turbo-machinery components, and austenitic and ferritic stainless steels for piping should be used in sCO2cycles. Exergy S.p.A. is focused to develop a new turbo-machinery for sCO2 in close-loop systems for direct heat exchange from green thermal sources, and in ICMATE Milan the nickel-base superalloy A286 that is widely used in aerospace applications, has been investigated through simulating the operational conditions of temperatures (560-720°C) and mechanical loadings (200-560 MPa) typical of sCO2 close-loop systems in order to test the alloy feasibility to be used in turbo-machinery components like shafts. Different production routes were also imposed to A286 by changing heat treatments and deformation conditions prior creep testing to find the optimal response of the alloy to the operational conditions. Results concerning the mechanical response and the microstructure evolution of A286 under creep conditions are reported.
Creep characterization of a nickel-based superalloy for sCO2 turbomachinery for green power generation
Angella G;Donnini R;Maldini M;Ripamonti D;
2018
Abstract
Thermodynamic cycles using CO2 in supercritical conditions (sCO2) can provide many advantages for future power generation applications. Thanks to the high fluid density, sCO2 causes a significant machinery size reduction, along with the possibility to achieve very good efficiencies. Due to thermal stability and non-flammability of sCO2, direct heat exchange from a wide range of thermal sources is possible from relatively low to very high temperatures. This makes sCO2 suitable for micro-channel-based heat exchanger technology in close-loop systems in combination with thermal solar power (CSP), biomass, flaring, nuclear and even geothermal sources. However, with sCO2material selection and design problems can raise, since materials must have resistance to high-temperature oxidation, corrosion and deformation under constant mechanical loading (creep resistance), so nickel-based superalloys for turbo-machinery components, and austenitic and ferritic stainless steels for piping should be used in sCO2cycles. Exergy S.p.A. is focused to develop a new turbo-machinery for sCO2 in close-loop systems for direct heat exchange from green thermal sources, and in ICMATE Milan the nickel-base superalloy A286 that is widely used in aerospace applications, has been investigated through simulating the operational conditions of temperatures (560-720°C) and mechanical loadings (200-560 MPa) typical of sCO2 close-loop systems in order to test the alloy feasibility to be used in turbo-machinery components like shafts. Different production routes were also imposed to A286 by changing heat treatments and deformation conditions prior creep testing to find the optimal response of the alloy to the operational conditions. Results concerning the mechanical response and the microstructure evolution of A286 under creep conditions are reported.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
