Based on dislocation reaction theory and Avrami equation, a constitutive equation model was developed to describe dynamic recovery and dynamic recrystallization during hot deformation of T122 heat resistant steel, whi...Based on dislocation reaction theory and Avrami equation, a constitutive equation model was developed to describe dynamic recovery and dynamic recrystallization during hot deformation of T122 heat resistant steel, which have taken the effect of dynamic strain aging into account. Uniaxial hot compression test had been carried out over a wide range of strain rate （0.01 to 10 s-1 ） and temperature （900 to 1 200 ~C） with the help of Gleeble 3500. Obtained experimental data was applied to determine the material parameters in proposed constitutive equations of T122 steel, by using the non-linear least square regress optimization method. The calculated constitutive equations are quantita- tively in good agreement with experimentally measured curves and microstructure observation. It shows that propose constitutive equation T122 steel is able to be used to predict flow stress of T122 steel during hot deformation in aus- tenite temperature scope.展开更多
T122 steel has been used to produce superheater or reheater of ultra supercritical boilers. With the help of chemical phase extraction and mierostructure characterization, the performance of aging precipitates of T122...T122 steel has been used to produce superheater or reheater of ultra supercritical boilers. With the help of chemical phase extraction and mierostructure characterization, the performance of aging precipitates of T122 steel, such as M23C6 carbide, Laves phase and MX phase was investigated, the strengthening mechanism of the steel was discussed, and the thermal yield stress of lath substructure, dislocations and precipitates of the steel were calculated. It was found that lath substructure and dislocations dominated the strengthening attribution and precipitation hardening went second to the strengthening attribution.展开更多
Ni-P-SiC_(P) coatings were deposited on 42CrMo steel by electroless plating.The surface morphologies and phase structures of the Ni-P-SiC_(P) coatings processed under different SiC_(P) concentrations at different heat...Ni-P-SiC_(P) coatings were deposited on 42CrMo steel by electroless plating.The surface morphologies and phase structures of the Ni-P-SiC_(P) coatings processed under different SiC_(P) concentrations at different heat treatment temperatures were analyzed.The microhardness,corrosion resistance,and wear resistance of the Ni-P-SiC_(P) coatings were studied.Results show that Ni-P-SiC_(P) coatings exhibit cauliflower-like morphology.Increasing the SiC_(P) concentration can reduce the size of cellular structure.The microhardness and corrosion resistance are initially increased and then decreased with the increase in SiC_(P) concentration.The maximum microhardness and corrosion potential are 7379 MPa and−0.363 V,respectively,when the SiC_(P) concentration is 5 g/L.The Ni-P-SiC_(P) coatings exhibit an amorphous structure,and the width of the diffuse diffraction peak becomes narrower with the increase in SiC_(P) concentration.It is suggested that SiC_(P) inhibits the deposition of P and promotes the microcrystalline transformation.After heat treatment at 350℃,the Ni-P-SiC_(P) coatings are crystallized,resulting in the precipitation of Ni3P phase.Heat treatment at 400℃ for 1 h maximizes the structure.The synergistic effect of the Ni3P precipitate phase and SiC_(P) dispersion phase promotes the densification of the cellular structure,leading to the optimal microhardness(13828 MPa),optimal corrosion resistance(−0.277 V),and excellent wear resistance.The wear mechanism is dominated by micro-cutting abrasive wear with slight adhesive and oxidative wear.展开更多
A new ferritic creep resistant steel has been developed by eliminating Nb and adding 1.5 mass % Re to a ferritic steel grade T/P23 with the aim of enhancing its mechanical properties at high temperature.Cast ingots of...A new ferritic creep resistant steel has been developed by eliminating Nb and adding 1.5 mass % Re to a ferritic steel grade T/P23 with the aim of enhancing its mechanical properties at high temperature.Cast ingots of both steels, new grade and ASTM T/P 23, were hot rolled at 900℃ and then submitted to a thermal treatment consisting of solubilization at 1050℃ and tempering at 700℃. Tempered bainitic microstructures obtained contain second phases reinforcing carbide particles, mainly M_6C and M_（23）C_6 at the boundaries of both, prior austenite grains and bainitic ferrite laths, as well as MC within the grains. Mechanical properties at temperatures ranging from 540 to 600℃ were studied by strain-ratechange tests in compression at strain rates between 10^（-7） and 10^（-4）s^（-1）. These tests showed high stress exponents（n ≥ 20） and activation energies（Q ≈ 400 k J/mol） for both alloys, which were associated with a dislocation movement mechanism with a strong interaction between dislocations and precipitates. On the other hand, a creep exponent of 5 was derived for the stress dependence of minimum creep rate from conventional-type creep tests at 600℃. Although this stress exponent is usually related to a dislocation climb controlled creep mechanism, remarkable microstructural degradation observed with increasing creep time makes difficult to elucidate the true deformation mechanism controlling creep.展开更多
基金Sponsored by National High-Tech Research and Development Program (863Program) of China (2003AA331060)
文摘Based on dislocation reaction theory and Avrami equation, a constitutive equation model was developed to describe dynamic recovery and dynamic recrystallization during hot deformation of T122 heat resistant steel, which have taken the effect of dynamic strain aging into account. Uniaxial hot compression test had been carried out over a wide range of strain rate （0.01 to 10 s-1 ） and temperature （900 to 1 200 ~C） with the help of Gleeble 3500. Obtained experimental data was applied to determine the material parameters in proposed constitutive equations of T122 steel, by using the non-linear least square regress optimization method. The calculated constitutive equations are quantita- tively in good agreement with experimentally measured curves and microstructure observation. It shows that propose constitutive equation T122 steel is able to be used to predict flow stress of T122 steel during hot deformation in aus- tenite temperature scope.
基金Item Sponsored by National Hi-Tech Research and Development Program of China (863 program) (2006AA03Z513)
文摘T122 steel has been used to produce superheater or reheater of ultra supercritical boilers. With the help of chemical phase extraction and mierostructure characterization, the performance of aging precipitates of T122 steel, such as M23C6 carbide, Laves phase and MX phase was investigated, the strengthening mechanism of the steel was discussed, and the thermal yield stress of lath substructure, dislocations and precipitates of the steel were calculated. It was found that lath substructure and dislocations dominated the strengthening attribution and precipitation hardening went second to the strengthening attribution.
基金Science Research Project of Handan Bureau of Science and Technology(21422075242)。
文摘Ni-P-SiC_(P) coatings were deposited on 42CrMo steel by electroless plating.The surface morphologies and phase structures of the Ni-P-SiC_(P) coatings processed under different SiC_(P) concentrations at different heat treatment temperatures were analyzed.The microhardness,corrosion resistance,and wear resistance of the Ni-P-SiC_(P) coatings were studied.Results show that Ni-P-SiC_(P) coatings exhibit cauliflower-like morphology.Increasing the SiC_(P) concentration can reduce the size of cellular structure.The microhardness and corrosion resistance are initially increased and then decreased with the increase in SiC_(P) concentration.The maximum microhardness and corrosion potential are 7379 MPa and−0.363 V,respectively,when the SiC_(P) concentration is 5 g/L.The Ni-P-SiC_(P) coatings exhibit an amorphous structure,and the width of the diffuse diffraction peak becomes narrower with the increase in SiC_(P) concentration.It is suggested that SiC_(P) inhibits the deposition of P and promotes the microcrystalline transformation.After heat treatment at 350℃,the Ni-P-SiC_(P) coatings are crystallized,resulting in the precipitation of Ni3P phase.Heat treatment at 400℃ for 1 h maximizes the structure.The synergistic effect of the Ni3P precipitate phase and SiC_(P) dispersion phase promotes the densification of the cellular structure,leading to the optimal microhardness(13828 MPa),optimal corrosion resistance(−0.277 V),and excellent wear resistance.The wear mechanism is dominated by micro-cutting abrasive wear with slight adhesive and oxidative wear.
基金supported by the Spanish Ministry of Economy and Competitiveness(MINECO)under Grant MAT2012-39124,MAT2015-68919,and MAT2016-80875
文摘A new ferritic creep resistant steel has been developed by eliminating Nb and adding 1.5 mass % Re to a ferritic steel grade T/P23 with the aim of enhancing its mechanical properties at high temperature.Cast ingots of both steels, new grade and ASTM T/P 23, were hot rolled at 900℃ and then submitted to a thermal treatment consisting of solubilization at 1050℃ and tempering at 700℃. Tempered bainitic microstructures obtained contain second phases reinforcing carbide particles, mainly M_6C and M_（23）C_6 at the boundaries of both, prior austenite grains and bainitic ferrite laths, as well as MC within the grains. Mechanical properties at temperatures ranging from 540 to 600℃ were studied by strain-ratechange tests in compression at strain rates between 10^（-7） and 10^（-4）s^（-1）. These tests showed high stress exponents（n ≥ 20） and activation energies（Q ≈ 400 k J/mol） for both alloys, which were associated with a dislocation movement mechanism with a strong interaction between dislocations and precipitates. On the other hand, a creep exponent of 5 was derived for the stress dependence of minimum creep rate from conventional-type creep tests at 600℃. Although this stress exponent is usually related to a dislocation climb controlled creep mechanism, remarkable microstructural degradation observed with increasing creep time makes difficult to elucidate the true deformation mechanism controlling creep.
