The oxide films of 316L and T91 exposed to 350-500℃ steam were investigated using transmission electron microscopy(TEM).Independent of the exposure temperature,a triplex oxide structure with outer magnetite,inner Cr-...The oxide films of 316L and T91 exposed to 350-500℃ steam were investigated using transmission electron microscopy(TEM).Independent of the exposure temperature,a triplex oxide structure with outer magnetite,inner Cr-rich(Fe_(1.4)Cr_(1.6)O_(4)),and Ni-rich layer formed on 316L,while only a duplex layer with outer magnetite and inner Cr-rich(Fe_(2.2)Cr_(0.8)O_(4))layer formed on T91.As the fast channels for oxidant and the obstacles for solid-state diffusion,nanopores are distributed evenly in the Cr-rich inner layer and are more abundant in 316L than in T91.The oxidation behavior of the materials was understood based on the microscopic characteristics of the oxide films.展开更多
At present, the main attention of researchers is paid to the deterioration of heat transfer when heating the outer surface of the pipe with the liquid or steam, flowing inside it, in the presence of films or deposits ...At present, the main attention of researchers is paid to the deterioration of heat transfer when heating the outer surface of the pipe with the liquid or steam, flowing inside it, in the presence of films or deposits on its inner surface. However, when pipe is heating by heat carrier medium, flowing inside it, film on the inner pipe surface serve a dual protective function, protecting the pipe from corrosion and reducing its thermal stress. The article represents the results of the computational analysis of protective films influence on the thermal stressed state of headers and steam pipelines of combined-cycle power plants (CCPP) heat-recovery steam generators at different transient operating conditions particularly at startups from different initial temperature states and thermal shock. It is shown that protective films have a significant influence on the stresses magnitude and damage accumulation mainly for great temperature disturbances (for thermal shock). Calculations were carried out at various thicknesses of films and assuming that their thermal conductivity less than thermal conductivity of the steam pipelines metal.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12005269 and U1832206).
文摘The oxide films of 316L and T91 exposed to 350-500℃ steam were investigated using transmission electron microscopy(TEM).Independent of the exposure temperature,a triplex oxide structure with outer magnetite,inner Cr-rich(Fe_(1.4)Cr_(1.6)O_(4)),and Ni-rich layer formed on 316L,while only a duplex layer with outer magnetite and inner Cr-rich(Fe_(2.2)Cr_(0.8)O_(4))layer formed on T91.As the fast channels for oxidant and the obstacles for solid-state diffusion,nanopores are distributed evenly in the Cr-rich inner layer and are more abundant in 316L than in T91.The oxidation behavior of the materials was understood based on the microscopic characteristics of the oxide films.
文摘At present, the main attention of researchers is paid to the deterioration of heat transfer when heating the outer surface of the pipe with the liquid or steam, flowing inside it, in the presence of films or deposits on its inner surface. However, when pipe is heating by heat carrier medium, flowing inside it, film on the inner pipe surface serve a dual protective function, protecting the pipe from corrosion and reducing its thermal stress. The article represents the results of the computational analysis of protective films influence on the thermal stressed state of headers and steam pipelines of combined-cycle power plants (CCPP) heat-recovery steam generators at different transient operating conditions particularly at startups from different initial temperature states and thermal shock. It is shown that protective films have a significant influence on the stresses magnitude and damage accumulation mainly for great temperature disturbances (for thermal shock). Calculations were carried out at various thicknesses of films and assuming that their thermal conductivity less than thermal conductivity of the steam pipelines metal.
