The effects of different aging processes on the precipitated phase,mechanical properties,molten salt corrosion resistance and post-weld microstructure of 347H stainless steel were studied.The results show that a large...The effects of different aging processes on the precipitated phase,mechanical properties,molten salt corrosion resistance and post-weld microstructure of 347H stainless steel were studied.The results show that a large number of precipitated phases appear in the crystal after aging at 700℃for 400 h.After aging for 3000 h,the number of precipitated phases increases and most of them are gathered at the grain boundaries.There are two forms of precipitates,one is the coarse precipitate rich in Cr,and the other is the smaller precipitates mainly consisting of NbC.After aging at 700℃for 30 min,the yield strength and tensile strength of the samples at room temperature and 593℃increase,but the elongation decreases.The corrosion results in nitrate at 565℃show that the corrosion products of the aged samples are the same as that of the original samples,which are Fe_(2)O_(3),Fe_(3)O_(4),MgCr_(2)O_(4),MgFe_(2)O_(4),FeCr_(2)O_(4) and NaFeO_(2).The proportion of Fe_(3)O_(4) that is dense and well bonded to the subtrate in the original sample is higher than that in the aged sample,so the corrosion resistance is better.At 700℃,the aging time has no obvious effect on the microstructure after welding.展开更多
A static corrosion experiment of 347H stainless steel alloyed with elements Cu and Mo was carried out in a nitrate molten salt(60%NaNO_(3)+40%KNO_(3))at 565℃ for 720 h.The effects of elements Cu and Mo on the corrosi...A static corrosion experiment of 347H stainless steel alloyed with elements Cu and Mo was carried out in a nitrate molten salt(60%NaNO_(3)+40%KNO_(3))at 565℃ for 720 h.The effects of elements Cu and Mo on the corrosion resistance of 347H stainless steel in molten salt were investigated by analyzing the phase composition,microstructure and chemical composition of the corrosion products.The results show that the grain refinement induced by element Mo imparts the stainless steel with optimal corrosion resistance at a medium grain size.Furthermore,the formation of MoC significantly enhances the intergranular corrosion resistance of the stainless steel.The stainless steel exhibits uniform corrosion in the nitrate solution.The corrosion layer displays a dual-layer structure,and the corrosion products protecting matrix are present in both the inner and outer layers.The outer layer consists of a mixture of Fe oxides(Fe_(2)O_(3),Fe_(3)O_(4)),NaFeO_(2),and a minor amount of MgFe_(2)O_(4).Conversely,the inner layer is primarily composed of a spinel layer(FeCr_(2)O_(4),MgCr_(2)O_(4))and a thin Cu_(2)O layer.The oxidation of Cu in the inner layer leads to the formation of a dense Cu_(2)O layer,effectively impeding O_(2)-plasma infiltration into the matrix.展开更多
基金Science and Technology Program Project of Gansu Province(21ZD3GB001)。
文摘The effects of different aging processes on the precipitated phase,mechanical properties,molten salt corrosion resistance and post-weld microstructure of 347H stainless steel were studied.The results show that a large number of precipitated phases appear in the crystal after aging at 700℃for 400 h.After aging for 3000 h,the number of precipitated phases increases and most of them are gathered at the grain boundaries.There are two forms of precipitates,one is the coarse precipitate rich in Cr,and the other is the smaller precipitates mainly consisting of NbC.After aging at 700℃for 30 min,the yield strength and tensile strength of the samples at room temperature and 593℃increase,but the elongation decreases.The corrosion results in nitrate at 565℃show that the corrosion products of the aged samples are the same as that of the original samples,which are Fe_(2)O_(3),Fe_(3)O_(4),MgCr_(2)O_(4),MgFe_(2)O_(4),FeCr_(2)O_(4) and NaFeO_(2).The proportion of Fe_(3)O_(4) that is dense and well bonded to the subtrate in the original sample is higher than that in the aged sample,so the corrosion resistance is better.At 700℃,the aging time has no obvious effect on the microstructure after welding.
基金Science and Technology Program Project of Gansu Province(21ZD3GB001)。
文摘A static corrosion experiment of 347H stainless steel alloyed with elements Cu and Mo was carried out in a nitrate molten salt(60%NaNO_(3)+40%KNO_(3))at 565℃ for 720 h.The effects of elements Cu and Mo on the corrosion resistance of 347H stainless steel in molten salt were investigated by analyzing the phase composition,microstructure and chemical composition of the corrosion products.The results show that the grain refinement induced by element Mo imparts the stainless steel with optimal corrosion resistance at a medium grain size.Furthermore,the formation of MoC significantly enhances the intergranular corrosion resistance of the stainless steel.The stainless steel exhibits uniform corrosion in the nitrate solution.The corrosion layer displays a dual-layer structure,and the corrosion products protecting matrix are present in both the inner and outer layers.The outer layer consists of a mixture of Fe oxides(Fe_(2)O_(3),Fe_(3)O_(4)),NaFeO_(2),and a minor amount of MgFe_(2)O_(4).Conversely,the inner layer is primarily composed of a spinel layer(FeCr_(2)O_(4),MgCr_(2)O_(4))and a thin Cu_(2)O layer.The oxidation of Cu in the inner layer leads to the formation of a dense Cu_(2)O layer,effectively impeding O_(2)-plasma infiltration into the matrix.
