Thermodynamic calculation, SEM (scanning electron microscopy), TEM(transmission electron microscopy), XRD (X-ray diffraction), phase extraction, and chemical analysiswere employed to study the phase stability and phas...Thermodynamic calculation, SEM (scanning electron microscopy), TEM(transmission electron microscopy), XRD (X-ray diffraction), phase extraction, and chemical analysiswere employed to study the phase stability and phase precipitation in a new Ni-Cr-Co basesuperalloy heat-treated at 704 and 760 ℃ for a long tune. The results show that the precipitates ofthis new alloy heat-treated at standard annealing condition and heat-treated at 704 and 760℃ for atime up to 2000 h are γ′, MC, M_(23)C_6, and M_6C, and η phase forms at grain boundaries and inmatrix of samples heat-treated at 760 ℃ as well. The mass fractions of γ′ (+η), MC, M_(23)C_6,and M_6C in all samples have no large changes with an increase in aging time, but γ′ precipitatesgrow obviously. The γ′-to-η transformation in the samples heat-treated at 760℃ took place withincreasing aging time. The η precipitates form a Widmanstaetten pattern and the γ′ phases haveremelted partly in the samples heat-treated at 760 ℃. The alloy maintains a better microstructuralstability during prolonged aging at 704 ℃, but a worse microstructural stability during prolongedaging at 760 ℃.展开更多
A new modified A-286 (15Cr-28Ni-1.5Mo-lW-2Ti-Nb-Al) (mass fraction) designated as GH871 is characterized by high strengths but low ductility at 650℃ stress rupture and also high crack propagation rates at 650℃ creep...A new modified A-286 (15Cr-28Ni-1.5Mo-lW-2Ti-Nb-Al) (mass fraction) designated as GH871 is characterized by high strengths but low ductility at 650℃ stress rupture and also high crack propagation rates at 650℃ creep and creep/fatigue interaction conditions. For improvement of ductility and crack propagation behaviour, a primary vacuum induction melting and followed electro-slag refining process (VIM+ESR) has been adopted instead of air melting and electro-slag refining process (AIM+ESR). Vacuum melted GH871 (VIM+ESR) can keep the high strength level of this alloy and improve the ductility and also decrease crack propagation rates by this alloy purification. It is a good combination of strengthening and toughening for the alloy improvement and development.展开更多
文摘Thermodynamic calculation, SEM (scanning electron microscopy), TEM(transmission electron microscopy), XRD (X-ray diffraction), phase extraction, and chemical analysiswere employed to study the phase stability and phase precipitation in a new Ni-Cr-Co basesuperalloy heat-treated at 704 and 760 ℃ for a long tune. The results show that the precipitates ofthis new alloy heat-treated at standard annealing condition and heat-treated at 704 and 760℃ for atime up to 2000 h are γ′, MC, M_(23)C_6, and M_6C, and η phase forms at grain boundaries and inmatrix of samples heat-treated at 760 ℃ as well. The mass fractions of γ′ (+η), MC, M_(23)C_6,and M_6C in all samples have no large changes with an increase in aging time, but γ′ precipitatesgrow obviously. The γ′-to-η transformation in the samples heat-treated at 760℃ took place withincreasing aging time. The η precipitates form a Widmanstaetten pattern and the γ′ phases haveremelted partly in the samples heat-treated at 760 ℃. The alloy maintains a better microstructuralstability during prolonged aging at 704 ℃, but a worse microstructural stability during prolongedaging at 760 ℃.
文摘A new modified A-286 (15Cr-28Ni-1.5Mo-lW-2Ti-Nb-Al) (mass fraction) designated as GH871 is characterized by high strengths but low ductility at 650℃ stress rupture and also high crack propagation rates at 650℃ creep and creep/fatigue interaction conditions. For improvement of ductility and crack propagation behaviour, a primary vacuum induction melting and followed electro-slag refining process (VIM+ESR) has been adopted instead of air melting and electro-slag refining process (AIM+ESR). Vacuum melted GH871 (VIM+ESR) can keep the high strength level of this alloy and improve the ductility and also decrease crack propagation rates by this alloy purification. It is a good combination of strengthening and toughening for the alloy improvement and development.
