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.
