Secondary dendrite orientation and wall thickness considerably affect the stress rupture life of thin-walled samples.However,the effect of the secondary dendrite orientation on the thickness debit effect of nickel-bas...Secondary dendrite orientation and wall thickness considerably affect the stress rupture life of thin-walled samples.However,the effect of the secondary dendrite orientation on the thickness debit effect of nickel-based single-crystal superalloys has not been thoroughly investigated until now.Owing to geometrical constraints,typical sheet samples cannot reveal the mechanism responsible for the thickness debit effect in turbine blades.This study examined the effect of secondary dendrite orientation on the thickness debit effect of nickel-based single-crystal superalloys at 1100℃/137 MPa in tubular samples.As the wall thickness decreased from 1.5 mm to 0.3 mm,the stress rupture life decreased from approximately 170 h to 64 h,demonstrating a noticeable thickness debit effect.Among the different secondary dendrite orientation areas,the variation in plastic deformation difference increased from 7%(1.5 mm)to 45%(0.5 mm)and subsequently decreased to 4%(0.3 mm).In thinner samples,the thickness contraction and microstructure evolution were more pronounced in the[100]areas than that in the[110]and[210]areas.The theoretical calculation quantitatively indicated that for the effective stress increased,the contribution of plastic deformation(45%)was slightly lower than that of oxidation(55%)in 0.3 mm samples;nevertheless,plastic deformation played a prominent role in 0.5,0.8,1,and 1.5 mm samples and increased from 61%(0.5 mm samples)to 85%(1.5 mm samples).In thinner samples,the larger plastic deformation in the secondary dendrite orientation of the[100]areas and oxidation increased the effective stress,resulting in a shorter rupture life.These findings are conducive to the structural optimization and performance improvement of turbine blades.展开更多
The abundancy of defect sinks in the microstructure of laser powder bed fusion(LPBF) processed austenitic stainless steels was found to be beneficial for helium resistance.In the current study,the influence of the nov...The abundancy of defect sinks in the microstructure of laser powder bed fusion(LPBF) processed austenitic stainless steels was found to be beneficial for helium resistance.In the current study,the influence of the novel microstructure in LPBF processed 304 L on the helium bubble growth behaviour was investigated using transmission electron microscopy in samples implanted with He^(+) ion and post-irradiation annealing treated at 600℃ for 1 h.Two variants of LPBF processed 304 L samples were used,one in as-built condition and the other solution-annealed.The comparison between the two samples indicated that the helium bubble growth was inhibited and remained stable in the as-built sample but coarsened significantly in the solution-annealed sample.The sub-grain boundaries and oxide nano-inclusions acted as defect sinks to trap helium atoms and inhibited the growth of helium bubble in the as-built sample under the post-irradiation annealing conditions used.展开更多
Nuclear power plays a key role as renewable energy in alleviating the worldwide energy shortage.The material degradation caused by high-temperature and high-flux neutron irradiation is the most concerning issue for nu...Nuclear power plays a key role as renewable energy in alleviating the worldwide energy shortage.The material degradation caused by high-temperature and high-flux neutron irradiation is the most concerning issue for nuclear reactor safety.A large number of He atoms produced through the(n,α)transmutation reaction diffuse and migrate in metals and accumulate to form He bubbles because of the extremely low solubility of He atoms in metal materials.The helium bubbles gather at the grain boundary or grain to cause swelling,hardening,embrittlement,and other damages to the in-core structural components.This paper mainly summarizes the research progress on He irradiation in steel and iron-based alloys,including the diffusion and accumulation of He atoms,the nucleation and growth of He bubbles,and the microstructure and macroscopic degradation of material performance caused by He irradiation.The mechanism of helium irradiation-induced corrosion in steel and iron-based alloys in recent years is reviewed as well.Moreover,the investigations on irradiation performance in additive manufactured stainless steels are summarized,and the mechanism of irradiation resistance is prospected.展开更多
The composition and morphology of a passive film formed on Ni-based alloy 690 with different surface conditions exposed to high-temperature,high-pressure aerated and deaerated deionized water vapor with different time...The composition and morphology of a passive film formed on Ni-based alloy 690 with different surface conditions exposed to high-temperature,high-pressure aerated and deaerated deionized water vapor with different time were characterized by using X-ray photoelectron spectroscopy(XPS)and atomic force microscopy(AFM)in this study.Shot peened,mechanical polishing and electro polishing were used to obtain different surface conditions.The film thickness remained constant after different exposure treatments,while the film layered structures were different.On specimens exposed to aerated water for 2 min and deaerated water for 1 h,Ni-rich oxide was identified in the outmost oxide films while Cr-rich oxide existed in inner layers.On specimens exposed to aerated water for 1 h,Cr-rich oxide with participating of Ni-and Fe-oxide was identified in all layers,while on specimens exposed to deaerated water for 2 min,Cr-rich oxide in all layers with participating of Ni-oxide was identified.Large oxide particles with a low density were found.The oxide particles were the biggest and least dense for electro polished specimen,whilest smallest and most dense for shot peened specimen.Oxidation for the same time,the surface was oxidized more pronounced in aerated water than in deaeated water.展开更多
基金financially supported by the Science Center for Gas Turbine Project(No.P2021-AB-Ⅳ-001-002).
文摘Secondary dendrite orientation and wall thickness considerably affect the stress rupture life of thin-walled samples.However,the effect of the secondary dendrite orientation on the thickness debit effect of nickel-based single-crystal superalloys has not been thoroughly investigated until now.Owing to geometrical constraints,typical sheet samples cannot reveal the mechanism responsible for the thickness debit effect in turbine blades.This study examined the effect of secondary dendrite orientation on the thickness debit effect of nickel-based single-crystal superalloys at 1100℃/137 MPa in tubular samples.As the wall thickness decreased from 1.5 mm to 0.3 mm,the stress rupture life decreased from approximately 170 h to 64 h,demonstrating a noticeable thickness debit effect.Among the different secondary dendrite orientation areas,the variation in plastic deformation difference increased from 7%(1.5 mm)to 45%(0.5 mm)and subsequently decreased to 4%(0.3 mm).In thinner samples,the thickness contraction and microstructure evolution were more pronounced in the[100]areas than that in the[110]and[210]areas.The theoretical calculation quantitatively indicated that for the effective stress increased,the contribution of plastic deformation(45%)was slightly lower than that of oxidation(55%)in 0.3 mm samples;nevertheless,plastic deformation played a prominent role in 0.5,0.8,1,and 1.5 mm samples and increased from 61%(0.5 mm samples)to 85%(1.5 mm samples).In thinner samples,the larger plastic deformation in the secondary dendrite orientation of the[100]areas and oxidation increased the effective stress,resulting in a shorter rupture life.These findings are conducive to the structural optimization and performance improvement of turbine blades.
基金sponsored by the National Natural Science Foundation of China(Grant No.52073176)。
文摘The abundancy of defect sinks in the microstructure of laser powder bed fusion(LPBF) processed austenitic stainless steels was found to be beneficial for helium resistance.In the current study,the influence of the novel microstructure in LPBF processed 304 L on the helium bubble growth behaviour was investigated using transmission electron microscopy in samples implanted with He^(+) ion and post-irradiation annealing treated at 600℃ for 1 h.Two variants of LPBF processed 304 L samples were used,one in as-built condition and the other solution-annealed.The comparison between the two samples indicated that the helium bubble growth was inhibited and remained stable in the as-built sample but coarsened significantly in the solution-annealed sample.The sub-grain boundaries and oxide nano-inclusions acted as defect sinks to trap helium atoms and inhibited the growth of helium bubble in the as-built sample under the post-irradiation annealing conditions used.
基金sponsored by the National Natural Science Foundation of China(Grant No.52073176)the Shenzhen International Cooperation Research Science and Technology Program(No.GJHZ20200731095203011).
文摘Nuclear power plays a key role as renewable energy in alleviating the worldwide energy shortage.The material degradation caused by high-temperature and high-flux neutron irradiation is the most concerning issue for nuclear reactor safety.A large number of He atoms produced through the(n,α)transmutation reaction diffuse and migrate in metals and accumulate to form He bubbles because of the extremely low solubility of He atoms in metal materials.The helium bubbles gather at the grain boundary or grain to cause swelling,hardening,embrittlement,and other damages to the in-core structural components.This paper mainly summarizes the research progress on He irradiation in steel and iron-based alloys,including the diffusion and accumulation of He atoms,the nucleation and growth of He bubbles,and the microstructure and macroscopic degradation of material performance caused by He irradiation.The mechanism of helium irradiation-induced corrosion in steel and iron-based alloys in recent years is reviewed as well.Moreover,the investigations on irradiation performance in additive manufactured stainless steels are summarized,and the mechanism of irradiation resistance is prospected.
基金financially supported by the National Natural Science Foundation of China(No.52073176)
文摘The composition and morphology of a passive film formed on Ni-based alloy 690 with different surface conditions exposed to high-temperature,high-pressure aerated and deaerated deionized water vapor with different time were characterized by using X-ray photoelectron spectroscopy(XPS)and atomic force microscopy(AFM)in this study.Shot peened,mechanical polishing and electro polishing were used to obtain different surface conditions.The film thickness remained constant after different exposure treatments,while the film layered structures were different.On specimens exposed to aerated water for 2 min and deaerated water for 1 h,Ni-rich oxide was identified in the outmost oxide films while Cr-rich oxide existed in inner layers.On specimens exposed to aerated water for 1 h,Cr-rich oxide with participating of Ni-and Fe-oxide was identified in all layers,while on specimens exposed to deaerated water for 2 min,Cr-rich oxide in all layers with participating of Ni-oxide was identified.Large oxide particles with a low density were found.The oxide particles were the biggest and least dense for electro polished specimen,whilest smallest and most dense for shot peened specimen.Oxidation for the same time,the surface was oxidized more pronounced in aerated water than in deaeated water.
