For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical a...For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure.In this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the DMWs.Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization.By applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of DMW.The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ interface.The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries.The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking.It is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.展开更多
The excessive use of nonrenewable energy has brought about serious greenhouse effect.Converting CO_(2) into high-value-added chemicals is undoubtedly the best choice to solve energy problems.Due to the excellent cost-...The excessive use of nonrenewable energy has brought about serious greenhouse effect.Converting CO_(2) into high-value-added chemicals is undoubtedly the best choice to solve energy problems.Due to the excellent cost-effectiveness and dramatic catalytic performance,nickel-based catalysts have been considered as the most promising candidates for the electrocatalytic CO_(2) reduction reaction(eCO_(2)RR).In this work,the electrocatalytic reduction mechanism of CO_(2) over Ni-based materials is reviewed.The strategies to improve the eCO_(2)RR performance are emphasized.Moreover,the research on Ni-based materials for syngas generation is briefly summarized.Finally,the prospects of nickel-based materials in the eCO_(2)RR are provided with the hope of improving transition-metal-based electrocatalysts for eCO_(2)RR in the future.展开更多
The Shima yield criterion used in finite element analysis for nickel-based superalloy powder compact during hot isostatic pressing(HIP) was modified through uniaxial compression experiments. The influence of cylindric...The Shima yield criterion used in finite element analysis for nickel-based superalloy powder compact during hot isostatic pressing(HIP) was modified through uniaxial compression experiments. The influence of cylindrical capsule characteristics on FGH4096M superalloy powder compact deformation and densification behavior during HIP was investigated through simulations and experiments. Results revealed the simulation shrinkage prediction fitted well with the experimental shrinkage including a maximum shrinkage error of 1.5%. It was shown that the axial shrinkage was 1.7% higher than radial shrinkage for a cylindrical capsule with the size of ∮50 mm × 100 mm due to the force arm difference along the axial and radial direction of the capsule. The stress deviated from the isostatic state in the capsule led to the uneven shrinkage and non-uniform densification of the powder compact. The ratio of the maximum radial displacement to axial displacement increased from0.47 to 0.75 with the capsule thickness increasing from 2 to 4 mm. The pressure transmission is related to the capsule thickness, the capsule material performance, and physical parameters in the HIP process.展开更多
The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solu...The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solution-treated samples. The coarsening and dissolution of γ' phase simulta-neously occurred at intermediate temperatures. In some areas, the primary precipitates became blunt and the adjacent ones were intercon-nected with each other via a diffuse neck, indicating a coarsening process of the primary γ' population. The coarsening was dominated by the precipitate agglomeration mechanism (PAM) rather than by the well-known Ostwald ripening mechanism. In other areas, the partial dissolu-tion of the γ' precipitates began to occur, spreading gradually from dendrite cores to interdendritic regions. In addition, a flower-like γ' struc-ture was developed during the subsolvus solution treatments. The observable long filaments composed of erraticly shaped precipitates were caused by the heterogeneous nucleation of the cooling precipitates during water quenching.展开更多
The coarsening behavior of γ' particles in a nickel-base superalloy FGH95 was investigated by means of experimental observations and growth kinetics calculations. The results show that when aging at 1000,1080 and...The coarsening behavior of γ' particles in a nickel-base superalloy FGH95 was investigated by means of experimental observations and growth kinetics calculations. The results show that when aging at 1000,1080 and 1140°C for different times,the relation of average particle size to time obeys the cube law ( a /2)3= kt,where k is 15.49 × 103,77.5 × 103 and 230.04 × 103 nm3/min,respectively. The particle size distributions are better fit to the LSW theoretical distributions when aging at 1000°C within 1440 min. The activation energy for γ' particles coarsening is determined to be 288.20±1.79 kJ/mol,which correlates well to the diffusion activation energies of Al,Ti,and Nb in the nickel matrix. This indicates that the coarsening of γ' particles is controlled by the diffusion of Al,Ti,and Nb in the nickel matrix. The coarsening kinetics of γ' particles in FGH95 is predicted as rt 3 = 1.04 × 10 16t exp[-(288200 ± 1790 )/RT].展开更多
Hot-corrosion behaviors of nickel-base superalloy and aluminide diffusion coating have been investigated in conditions of contents of Na2SO4 and NaCI molten salts at 900℃ by means of XRD and SEM. Hot-corrosion scale ...Hot-corrosion behaviors of nickel-base superalloy and aluminide diffusion coating have been investigated in conditions of contents of Na2SO4 and NaCI molten salts at 900℃ by means of XRD and SEM. Hot-corrosion scale of the superalloy and aluminide diffusion coating were analyzed and their surface morphologies were observed. The results demonstrate that both coated and uncoated specimens are not susceptible to various contents of NaCI. That may be resulted from the AI2O3 scale formation. Growth stress was characterized by the formation of convoluted scales.展开更多
Selective laser melting(SLM),an additive manufacturing process mostly applied in the metal material field,can fabricate complex-shaped metal objects with high precision.Nickel-based superalloy exhibits excellent mecha...Selective laser melting(SLM),an additive manufacturing process mostly applied in the metal material field,can fabricate complex-shaped metal objects with high precision.Nickel-based superalloy exhibits excellent mechanical properties at elevated temperatures and plays an important role in the aviation industry.This paper emphasizes the research of SLM processed Inconel 718,Inconel 625,CM247LC,and Hastelloy X,which are typical alloys with different strengthening mechanisms and operating temperatures.The strengthening mechanism and phase change evolution of different nickel-based superalloys under laser irradiation are discussed.The influence of laser parameters and the heat-treatment process on mechanical properties of SLM nickel-based superalloys are systematically introduced.Moreover,the attractive in-dustrial applications of SLM nickel-based superalloy and printed components are presented.Finally,the prospects for nickel-based superalloy materials for SLM technology are presented.展开更多
The service performance of the turbine blade root of an aero-engine depends on the microstructures in its superficial layer.This work investigated the surface deformation structures of turbine blade root of single cry...The service performance of the turbine blade root of an aero-engine depends on the microstructures in its superficial layer.This work investigated the surface deformation structures of turbine blade root of single crystal nickel-based superalloy produced under different creep feed grinding conditions.Gradient microstructures in the superficial layer were clarified and composed of a severely deformed layer(DFL)with nano-sized grains(48–67 nm)at the topmost surface,a DFL with submicron-sized grains(66–158 nm)and micron-sized laminated structures at the subsurface,and a dislocation accumulated layer extending to the bulk material.The formation of such gradient microstructures was found to be related to the graded variations in the plastic strain and strain rate induced in the creep feed grinding process,which were as high as 6.67 and 8.17×10^(7)s^(−1),respectively.In the current study,the evolution of surface gradient microstructures was essentially a transition process from a coarse single crystal to nano-sized grains and,simultaneously,from one orientation of a single crystal to random orientations of polycrystals,during which the dislocation slips dominated the creep feed grinding induced microstructure deformation of single crystal nickel-based superalloy.展开更多
In order to enhance the high-temperature stress rupture strength of brazing seam by heat treatment, it was diffusion treated, then solution heat treated, and finally aging treated. The microstructure of brazing seam e...In order to enhance the high-temperature stress rupture strength of brazing seam by heat treatment, it was diffusion treated, then solution heat treated, and finally aging treated. The microstructure of brazing seam especially morphology of y’ phase and boride was observed and the strength of brazing seam was measured in this process. The results show that heat treatment can enhance high- temperature stress rupture strength by improving the microstructure of brazing seam. The strength of brazing seam after solution heat treatment decreases in comparison with that only after diffusion treatment while aging treatment after solution heat treatment increases the strength of brazing seam.展开更多
The nickel-based coating with different TiC addition was fabricated onto 45 steel substrate by using induction brazed technology in air.The effect of TiC addition on the microstructure and wear resistance of induction...The nickel-based coating with different TiC addition was fabricated onto 45 steel substrate by using induction brazed technology in air.The effect of TiC addition on the microstructure and wear resistance of induction brazing coating was studied.The results show that the microstructure of brazing coating is strengthened and refined by adding TiC.With the increase of the amount of TiC added,the amount of TiC in the Ni-based matrix is increased,and the matrix structure is obviously refined.This is because the high melting point TiC particles can be used as heterogeneous nucleation cores,thus refining the Ni based matrix structure.Moreover,the wear resistance of brazing coating is improved due to the addition of TiC.展开更多
The advanced ultra-supercritical power plants of the future will utilize steam pressures and temperatures that are too high for traditional ferritic steels,thus requiring austenitic materials.Older nickel-base superal...The advanced ultra-supercritical power plants of the future will utilize steam pressures and temperatures that are too high for traditional ferritic steels,thus requiring austenitic materials.Older nickel-base superalloys such as 263 and 617 were initially evaluated under the European THERMIE project beginning in the 1990s.An entirely new age-hardened alloy 740 which possesses exceptional fireside corrosion resistance and creep strength was also developed for boiler tubing capable of serving at 700C.Subsequently,interest in the USA considered other product forms such as steam header piping and steam turbine forgings for service as high as 760C.A more stable and weldable alloy version now called 740H was developed to meet these more demanding conditions.This paper summarizes the current status of work on alloys 740 and 740H.展开更多
The 3d transition-metal nickel(Ni)-based cathodes have long been widely used in rechargeable batteries for over 100 years,from Ni-based alkaline rechargeable batteries,such as nickel-cadmium(Ni-Cd)and nickel-metal hyd...The 3d transition-metal nickel(Ni)-based cathodes have long been widely used in rechargeable batteries for over 100 years,from Ni-based alkaline rechargeable batteries,such as nickel-cadmium(Ni-Cd)and nickel-metal hydride(Ni-MH)batteries,to the Ni-rich cathode featured in lithium-ion batteries(LIBs).Ni-based alkaline batteries were first invented in the 1900s,and the well-developed Ni-MH batteries were used on a large scale in Toyota Prius vehicles in the mid-1990s.Around the same time,however,Sony Corporation commercialized the first LIBs in camcorders.After temporally fading as LiCoO_(2) dominated the cathode in LIBs,nickel oxide-based cathodes eventually found their way back to the mainstreaming battery industry.The uniqueness of Ni in batteries is that it helps to deliver high energy density and great storage capacity at a low cost.This review mainly provides a comprehensive overview of the key role of Ni-based cathodes in rechargeable batteries.After presenting the physical and chemical properties of the 3d transition-metal Ni,which make it an optimal cationic redox center in the cathode of batteries,we introduce the structure,reaction mechanism,and modification of nickel hydroxide electrode in Ni-Cd and Ni-MH rechargeable batteries.We then move on to the Ni-based layered oxide cathode in LIBs,with a focus on the structure,issues,and challenges of layered oxides,LiNiO_(2),and LiNi_(1−x−y)Co_(x)Mn_(y)O_(2).The role of Ni in the electrochemical performance and thermal stability of the Ni-rich cathode is highlighted.By bridging the“old”Ni-based batteries and the“modern”Ni-rich cathode in the LIBs,this review is committed to providing insights into the Ni-based electrochemistry and material design,which have been under research and development for over 100 years.This overview would shed new light on the development of advanced Ni-containing batteries with high energy density and long cycle life.展开更多
Grain growth, mechanical properties, and fracture mechanism of nickel-based GH4099 superalloy are investigated using heat treatments, tensile tests, optical microscopy (OM), and scanning electron microscopy (SEM) with...Grain growth, mechanical properties, and fracture mechanism of nickel-based GH4099 superalloy are investigated using heat treatments, tensile tests, optical microscopy (OM), and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). The OM observation shows that the matrix grains (γ-grains) undergo an apparent growth during the solution treatment. The grain size diameter increases from 100 to 174 μm when the solution temperature rises from 1100℃ to 1160℃ for 30 min. When the holding time increases from 15 to 60 min at 1140℃, the grain size diameter increases from 140 to 176 μm, indicating that the γ-grain growth is more sensitive to temperature than time. Standard deviation, <em>S</em><sub>v</sub>, and the grain size distribution are utilized to characterize the microstructural uniformity. To predict the grain size more accurately, we develop the grain growth kinetics and find that the growth index is close to 5. The yield strength (<em>R</em><sub>p0.2</sub>), tensile strength (<em>R</em><sub>m</sub>), and ductility (<em>A</em><sub>f</sub>) are also measured. It is found that the effect decreases in the order cooling rate, solution temperature, time. <em>R</em><sub>p0.2</sub> reduces by 47% with the increase in the cooling rate from 1℃ to 8000℃/min, while both strength and ductility exhibit little changes with time. The SEM results show that the fracture surfaces have typical mixed brittle and ductile characteristics when specimens are subjected to water quenching and air cooling. However, a complete brittle fracture occurs under furnace cooling conditions. The EDS analysis indicates that the brittle γ' (Ni<sub>3</sub>Ti) phase precipitates around the γ-grain boundary during the slow cooling process, which is the main factor yielding the complete brittle fracture. Finally, the optimal solution treatment scheme for the GH4099 superalloy is proposed—a temperature of 1140℃ for 30 min followed by air cooling.展开更多
Hot cracking susceptibility of fillers 52 and 82 in 800H and 825 nickel-base superalloys was discussed using the Spot Varestraint test.The fillers of 52 and 82 were added into nickel-base superalloys via a gas tungste...Hot cracking susceptibility of fillers 52 and 82 in 800H and 825 nickel-base superalloys was discussed using the Spot Varestraint test.The fillers of 52 and 82 were added into nickel-base superalloys via a gas tungsten arc welding(GTAW).Experimental results showed that the hot cracking sensitivity of the nickel-base superalloys with filler at high temperature was lower than that without filler.The hot cracking sensitivity had a slight effect when the filler 82 was added.The total length of crack was increased,the liquid-solid(L-S)two-phase range is higher so that the hot cracking susceptibility will be raised.The morphologies of cracks included the intergranular crack in the molten pool,molten pool of solidification cracking,heat-affected zone of intergranular cracks,and transgranular crack in the heat-affected zone.展开更多
The nickel-base alloy is one of the leading candidate materials for generation IV nuclear reactor pressure vessel.To evaluate its stability of helium damage and retention,helium ions with different energy of 80 keV an...The nickel-base alloy is one of the leading candidate materials for generation IV nuclear reactor pressure vessel.To evaluate its stability of helium damage and retention,helium ions with different energy of 80 keV and 180 keV were introduced by ion implantation to a certain dose(peak displacement damage 1-10 dpa).Then thermal desorption spectroscopy(TDS)of helium atoms was performed to discuss the helium desorption characteristic and trapping sites.The desorption peaks shift to a lower temperature with increasing dpa for both 80 keV and 180 keV irradiation,reflecting the reduced diffusion activation energy and faster diffusion within the alloy.The main release peak temperature of 180 keV helium injection is relatively higher than that of 80 keV at the same influence,which is because the irradiation damage of 180 keV,helium formation and entrapment occur deeper.The broadening of the spectra corresponds to different helium trapping sites(He-vacancies,grain boundary)and desorption mechanisms(different Hen Vm size).The helium retention amount of 80 keV is lower than that of 180 keV,and a saturation limit associated with the irradiation of 80 keV has been reached.The relatively low helium retention proves the better resistance to helium bubbles formation and helium brittleness.展开更多
The creep and rupture behavior of a nickel-base single crystal superalloy with [001] orientation was investigated at temperature of 10001040℃ and stress in the range of 150320MPa. The creep features and micro...The creep and rupture behavior of a nickel-base single crystal superalloy with [001] orientation was investigated at temperature of 10001040℃ and stress in the range of 150320MPa. The creep features and microstructure were studied by means of the measurement of creep curves and TEM observation. The results show that all creep curves exhibit a short primary and a dominant accelerated creep stage. From the creep parameters and TEM observations, it is suggested that the primary deformation mechanism has a change from precipitatation shearing by pairs of dislocation in the high applied stress region to dislocations climb around the γ′ particles in the low applied stress region. Furthermore, the detailed failure process and fracture surfaces were analyzed by SEM observation.展开更多
Evaluating the recyclability of powders in additive manufacturing has been a long-term challenge.In this study,the microstructure and mechanical properties of a nickel-based superalloy fabricated by laser powder-bed f...Evaluating the recyclability of powders in additive manufacturing has been a long-term challenge.In this study,the microstructure and mechanical properties of a nickel-based superalloy fabricated by laser powder-bed fusion(LPBF)using recycled powders were investigated.Re-melted powder surfaces,satellite particles,and deformed powders were found in the recycled powders,combined with a high-oxygencontent surface layer.The increasing oxygen content led to the formation of high-density oxide inclusions;moreover,printing-induced cracks widely occurred and mainly formed along the grain boundaries in the as-built LPBF nickel-based superalloys fabricated using recycled powders.A little change in the Si or Mn content did not increase the hot cracking susceptibility(HCS)of the printed parts.The changing aspect ratio and the surface damage of the recycled powders might contribute to increasing the crack density.Moreover,the configuration of cracks in the as-built parts led to anisotropic mechanical properties,mainly resulting in extremely low ductility vertical to the building direction,and the cracks mainly propagated along the cellular boundary owing to the existence of a brittle precipitation phase.展开更多
Heavy elements(X=Ta/W/Re)play an important role in the performance of superalloys,which enhance the strength,anti-oxidation,creep resistance,and anti-corrosiveness of alloy materials in a high-temperature environment....Heavy elements(X=Ta/W/Re)play an important role in the performance of superalloys,which enhance the strength,anti-oxidation,creep resistance,and anti-corrosiveness of alloy materials in a high-temperature environment.In the present research,the heavy element doping effects in FCC-Ni(γ)and Ni_(3)Al(γ')systems are investigated in terms of their thermodynamic and mechanical properties,as well as electronic structures.The lattice constant,bulk modulus,elastic constant,and dopant formation energy in non-spin,spin polarized,and spin-orbit coupling(SOC)calculations are compared.The results show that the SOC effects are important in accurate electronic structure calculations for alloys with heavy elements.We find that including spin for bothγandγ'phases is necessary and sufficient for most cases,but the dopant formation energy is sensitive to different spin effects,for instance,in the absence of SOC,even spin-polarized calculations give 1%to 9%variance in the dopant formation energy in our model.Electronic structures calculations indicate that spin polarization causes a split in the metal d states,and SOC introduces a variance in the spin-up and spin-down states of the d states of heavy metals and reduces the magnetic moment of the system.展开更多
基金Supported by Youth Elite Project of CNNC and Modular HTGR Super-critical Power Generation Technology Collaborative Project between CNNC and Tsinghua University Project of China(Grant No.ZHJTIZYFGWD20201).
文摘For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure.In this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the DMWs.Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization.By applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of DMW.The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ interface.The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries.The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking.It is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.
基金support from the National Natural Science Foundation of China(52072389,52311530113)the Science and Technology Commission of Shanghai Municipality(22DZ1205600,20520760900)+2 种基金the Program of Shanghai Academic Research Leader(20XD1424300)for financial support.The authors also would like to express their gratitude to Tangshan Basic Research Funding Projects(23130210E),Hebei Province High-level Talent(Postdoctor)Funding Project(B2022003025)Key R&D projects of North China University of Science and Technology(ZD-ST-202301)Tangshan Talent Funding Project(A202202007)for their financial support.
文摘The excessive use of nonrenewable energy has brought about serious greenhouse effect.Converting CO_(2) into high-value-added chemicals is undoubtedly the best choice to solve energy problems.Due to the excellent cost-effectiveness and dramatic catalytic performance,nickel-based catalysts have been considered as the most promising candidates for the electrocatalytic CO_(2) reduction reaction(eCO_(2)RR).In this work,the electrocatalytic reduction mechanism of CO_(2) over Ni-based materials is reviewed.The strategies to improve the eCO_(2)RR performance are emphasized.Moreover,the research on Ni-based materials for syngas generation is briefly summarized.Finally,the prospects of nickel-based materials in the eCO_(2)RR are provided with the hope of improving transition-metal-based electrocatalysts for eCO_(2)RR in the future.
基金financially supported by Guangdong Province Key Field R&D Program, China (No. 2019B01 0935001)the National Nature Science Foundation of China (No. 51905192)the Fundamental Research Funds for the Central Universities (No. FRT-TP-20-006A2)
文摘The Shima yield criterion used in finite element analysis for nickel-based superalloy powder compact during hot isostatic pressing(HIP) was modified through uniaxial compression experiments. The influence of cylindrical capsule characteristics on FGH4096M superalloy powder compact deformation and densification behavior during HIP was investigated through simulations and experiments. Results revealed the simulation shrinkage prediction fitted well with the experimental shrinkage including a maximum shrinkage error of 1.5%. It was shown that the axial shrinkage was 1.7% higher than radial shrinkage for a cylindrical capsule with the size of ∮50 mm × 100 mm due to the force arm difference along the axial and radial direction of the capsule. The stress deviated from the isostatic state in the capsule led to the uneven shrinkage and non-uniform densification of the powder compact. The ratio of the maximum radial displacement to axial displacement increased from0.47 to 0.75 with the capsule thickness increasing from 2 to 4 mm. The pressure transmission is related to the capsule thickness, the capsule material performance, and physical parameters in the HIP process.
基金supported by the Aviation Industry Corporation of China (No. 201110026-01)
文摘The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solution-treated samples. The coarsening and dissolution of γ' phase simulta-neously occurred at intermediate temperatures. In some areas, the primary precipitates became blunt and the adjacent ones were intercon-nected with each other via a diffuse neck, indicating a coarsening process of the primary γ' population. The coarsening was dominated by the precipitate agglomeration mechanism (PAM) rather than by the well-known Ostwald ripening mechanism. In other areas, the partial dissolu-tion of the γ' precipitates began to occur, spreading gradually from dendrite cores to interdendritic regions. In addition, a flower-like γ' struc-ture was developed during the subsolvus solution treatments. The observable long filaments composed of erraticly shaped precipitates were caused by the heterogeneous nucleation of the cooling precipitates during water quenching.
基金the National Natural Science Foundation of China (No. 50471097)the Programme of Introducing Talents of Discipline to Chinese Universities (No. B07003).
文摘The coarsening behavior of γ' particles in a nickel-base superalloy FGH95 was investigated by means of experimental observations and growth kinetics calculations. The results show that when aging at 1000,1080 and 1140°C for different times,the relation of average particle size to time obeys the cube law ( a /2)3= kt,where k is 15.49 × 103,77.5 × 103 and 230.04 × 103 nm3/min,respectively. The particle size distributions are better fit to the LSW theoretical distributions when aging at 1000°C within 1440 min. The activation energy for γ' particles coarsening is determined to be 288.20±1.79 kJ/mol,which correlates well to the diffusion activation energies of Al,Ti,and Nb in the nickel matrix. This indicates that the coarsening of γ' particles is controlled by the diffusion of Al,Ti,and Nb in the nickel matrix. The coarsening kinetics of γ' particles in FGH95 is predicted as rt 3 = 1.04 × 10 16t exp[-(288200 ± 1790 )/RT].
文摘Hot-corrosion behaviors of nickel-base superalloy and aluminide diffusion coating have been investigated in conditions of contents of Na2SO4 and NaCI molten salts at 900℃ by means of XRD and SEM. Hot-corrosion scale of the superalloy and aluminide diffusion coating were analyzed and their surface morphologies were observed. The results demonstrate that both coated and uncoated specimens are not susceptible to various contents of NaCI. That may be resulted from the AI2O3 scale formation. Growth stress was characterized by the formation of convoluted scales.
基金the National Nat-ural Science Foundation of China(No.51901020)Shan-dong Key Research and Development Plan Project(No.2019JZZY010327)+1 种基金Aeronautical Science Foundation of China(No.201942074001)the Fundamental Research Funds for the Central Universities,University of Science and Technology Beijing(No.FRF-IP-20-05).
文摘Selective laser melting(SLM),an additive manufacturing process mostly applied in the metal material field,can fabricate complex-shaped metal objects with high precision.Nickel-based superalloy exhibits excellent mechanical properties at elevated temperatures and plays an important role in the aviation industry.This paper emphasizes the research of SLM processed Inconel 718,Inconel 625,CM247LC,and Hastelloy X,which are typical alloys with different strengthening mechanisms and operating temperatures.The strengthening mechanism and phase change evolution of different nickel-based superalloys under laser irradiation are discussed.The influence of laser parameters and the heat-treatment process on mechanical properties of SLM nickel-based superalloys are systematically introduced.Moreover,the attractive in-dustrial applications of SLM nickel-based superalloy and printed components are presented.Finally,the prospects for nickel-based superalloy materials for SLM technology are presented.
基金This work was financially supported by the National Nat-ural Science Foundation of China(Nos.51921003,51775275 and 51905363)the Natural Science Foundation of Jiangsu Province(No.BK20190940)+1 种基金the National Major Science and Technology Projects of China(No.2017-VII-0002-0095)the Six Talents Summit Project in Jiangsu Province(No.JXQC-002).
文摘The service performance of the turbine blade root of an aero-engine depends on the microstructures in its superficial layer.This work investigated the surface deformation structures of turbine blade root of single crystal nickel-based superalloy produced under different creep feed grinding conditions.Gradient microstructures in the superficial layer were clarified and composed of a severely deformed layer(DFL)with nano-sized grains(48–67 nm)at the topmost surface,a DFL with submicron-sized grains(66–158 nm)and micron-sized laminated structures at the subsurface,and a dislocation accumulated layer extending to the bulk material.The formation of such gradient microstructures was found to be related to the graded variations in the plastic strain and strain rate induced in the creep feed grinding process,which were as high as 6.67 and 8.17×10^(7)s^(−1),respectively.In the current study,the evolution of surface gradient microstructures was essentially a transition process from a coarse single crystal to nano-sized grains and,simultaneously,from one orientation of a single crystal to random orientations of polycrystals,during which the dislocation slips dominated the creep feed grinding induced microstructure deformation of single crystal nickel-based superalloy.
文摘In order to enhance the high-temperature stress rupture strength of brazing seam by heat treatment, it was diffusion treated, then solution heat treated, and finally aging treated. The microstructure of brazing seam especially morphology of y’ phase and boride was observed and the strength of brazing seam was measured in this process. The results show that heat treatment can enhance high- temperature stress rupture strength by improving the microstructure of brazing seam. The strength of brazing seam after solution heat treatment decreases in comparison with that only after diffusion treatment while aging treatment after solution heat treatment increases the strength of brazing seam.
基金supported by the 2020 Ningbo“3315 Talent Introduction Plan”Innovative Team(C-Class)the major project of Ningbo“Scientific and Technological Innovation 2025”(Grant No.2020Z111)Science and Technology Major Project of Zhejiang Province(No.203ZP20220161)。
文摘The nickel-based coating with different TiC addition was fabricated onto 45 steel substrate by using induction brazed technology in air.The effect of TiC addition on the microstructure and wear resistance of induction brazing coating was studied.The results show that the microstructure of brazing coating is strengthened and refined by adding TiC.With the increase of the amount of TiC added,the amount of TiC in the Ni-based matrix is increased,and the matrix structure is obviously refined.This is because the high melting point TiC particles can be used as heterogeneous nucleation cores,thus refining the Ni based matrix structure.Moreover,the wear resistance of brazing coating is improved due to the addition of TiC.
文摘The advanced ultra-supercritical power plants of the future will utilize steam pressures and temperatures that are too high for traditional ferritic steels,thus requiring austenitic materials.Older nickel-base superalloys such as 263 and 617 were initially evaluated under the European THERMIE project beginning in the 1990s.An entirely new age-hardened alloy 740 which possesses exceptional fireside corrosion resistance and creep strength was also developed for boiler tubing capable of serving at 700C.Subsequently,interest in the USA considered other product forms such as steam header piping and steam turbine forgings for service as high as 760C.A more stable and weldable alloy version now called 740H was developed to meet these more demanding conditions.This paper summarizes the current status of work on alloys 740 and 740H.
基金financially supported by the China Postdoctoral Science Foundation(No.2021M700396)the National Natural Science Foundation of China(No.52102206)。
文摘The 3d transition-metal nickel(Ni)-based cathodes have long been widely used in rechargeable batteries for over 100 years,from Ni-based alkaline rechargeable batteries,such as nickel-cadmium(Ni-Cd)and nickel-metal hydride(Ni-MH)batteries,to the Ni-rich cathode featured in lithium-ion batteries(LIBs).Ni-based alkaline batteries were first invented in the 1900s,and the well-developed Ni-MH batteries were used on a large scale in Toyota Prius vehicles in the mid-1990s.Around the same time,however,Sony Corporation commercialized the first LIBs in camcorders.After temporally fading as LiCoO_(2) dominated the cathode in LIBs,nickel oxide-based cathodes eventually found their way back to the mainstreaming battery industry.The uniqueness of Ni in batteries is that it helps to deliver high energy density and great storage capacity at a low cost.This review mainly provides a comprehensive overview of the key role of Ni-based cathodes in rechargeable batteries.After presenting the physical and chemical properties of the 3d transition-metal Ni,which make it an optimal cationic redox center in the cathode of batteries,we introduce the structure,reaction mechanism,and modification of nickel hydroxide electrode in Ni-Cd and Ni-MH rechargeable batteries.We then move on to the Ni-based layered oxide cathode in LIBs,with a focus on the structure,issues,and challenges of layered oxides,LiNiO_(2),and LiNi_(1−x−y)Co_(x)Mn_(y)O_(2).The role of Ni in the electrochemical performance and thermal stability of the Ni-rich cathode is highlighted.By bridging the“old”Ni-based batteries and the“modern”Ni-rich cathode in the LIBs,this review is committed to providing insights into the Ni-based electrochemistry and material design,which have been under research and development for over 100 years.This overview would shed new light on the development of advanced Ni-containing batteries with high energy density and long cycle life.
文摘Grain growth, mechanical properties, and fracture mechanism of nickel-based GH4099 superalloy are investigated using heat treatments, tensile tests, optical microscopy (OM), and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). The OM observation shows that the matrix grains (γ-grains) undergo an apparent growth during the solution treatment. The grain size diameter increases from 100 to 174 μm when the solution temperature rises from 1100℃ to 1160℃ for 30 min. When the holding time increases from 15 to 60 min at 1140℃, the grain size diameter increases from 140 to 176 μm, indicating that the γ-grain growth is more sensitive to temperature than time. Standard deviation, <em>S</em><sub>v</sub>, and the grain size distribution are utilized to characterize the microstructural uniformity. To predict the grain size more accurately, we develop the grain growth kinetics and find that the growth index is close to 5. The yield strength (<em>R</em><sub>p0.2</sub>), tensile strength (<em>R</em><sub>m</sub>), and ductility (<em>A</em><sub>f</sub>) are also measured. It is found that the effect decreases in the order cooling rate, solution temperature, time. <em>R</em><sub>p0.2</sub> reduces by 47% with the increase in the cooling rate from 1℃ to 8000℃/min, while both strength and ductility exhibit little changes with time. The SEM results show that the fracture surfaces have typical mixed brittle and ductile characteristics when specimens are subjected to water quenching and air cooling. However, a complete brittle fracture occurs under furnace cooling conditions. The EDS analysis indicates that the brittle γ' (Ni<sub>3</sub>Ti) phase precipitates around the γ-grain boundary during the slow cooling process, which is the main factor yielding the complete brittle fracture. Finally, the optimal solution treatment scheme for the GH4099 superalloy is proposed—a temperature of 1140℃ for 30 min followed by air cooling.
基金The authors are obligated to thank the Ministry and Science and Technology(MOST)of the Taiwan,R.O.C.for the financial support under the projects numbered MOST 103-2218-E-005-002.
文摘Hot cracking susceptibility of fillers 52 and 82 in 800H and 825 nickel-base superalloys was discussed using the Spot Varestraint test.The fillers of 52 and 82 were added into nickel-base superalloys via a gas tungsten arc welding(GTAW).Experimental results showed that the hot cracking sensitivity of the nickel-base superalloys with filler at high temperature was lower than that without filler.The hot cracking sensitivity had a slight effect when the filler 82 was added.The total length of crack was increased,the liquid-solid(L-S)two-phase range is higher so that the hot cracking susceptibility will be raised.The morphologies of cracks included the intergranular crack in the molten pool,molten pool of solidification cracking,heat-affected zone of intergranular cracks,and transgranular crack in the heat-affected zone.
基金Project supported by Special Funds for Fundamental Research Funds for Central Universities,China(Grant Nos.2018 NTST29 and 2018 NTST04)the National Natural Science Foundation of China(Grant No.61176003)+1 种基金Chinese Postdoctoral Science Foundation(Grant No.2019M650524)Guangdong Province Key Area R&D Program,China(Grant No.2019B090909002)。
文摘The nickel-base alloy is one of the leading candidate materials for generation IV nuclear reactor pressure vessel.To evaluate its stability of helium damage and retention,helium ions with different energy of 80 keV and 180 keV were introduced by ion implantation to a certain dose(peak displacement damage 1-10 dpa).Then thermal desorption spectroscopy(TDS)of helium atoms was performed to discuss the helium desorption characteristic and trapping sites.The desorption peaks shift to a lower temperature with increasing dpa for both 80 keV and 180 keV irradiation,reflecting the reduced diffusion activation energy and faster diffusion within the alloy.The main release peak temperature of 180 keV helium injection is relatively higher than that of 80 keV at the same influence,which is because the irradiation damage of 180 keV,helium formation and entrapment occur deeper.The broadening of the spectra corresponds to different helium trapping sites(He-vacancies,grain boundary)and desorption mechanisms(different Hen Vm size).The helium retention amount of 80 keV is lower than that of 180 keV,and a saturation limit associated with the irradiation of 80 keV has been reached.The relatively low helium retention proves the better resistance to helium bubbles formation and helium brittleness.
文摘The creep and rupture behavior of a nickel-base single crystal superalloy with [001] orientation was investigated at temperature of 10001040℃ and stress in the range of 150320MPa. The creep features and microstructure were studied by means of the measurement of creep curves and TEM observation. The results show that all creep curves exhibit a short primary and a dominant accelerated creep stage. From the creep parameters and TEM observations, it is suggested that the primary deformation mechanism has a change from precipitatation shearing by pairs of dislocation in the high applied stress region to dislocations climb around the γ′ particles in the low applied stress region. Furthermore, the detailed failure process and fracture surfaces were analyzed by SEM observation.
基金This work was financially supported by the National Key Research and Development Program of China(No.2017YFB 0702300)the National Natural Science Foundation of China(No.51871028)the Fundamental Research Funds for the Central Universities(No.FRF-TP-19-003B2).
文摘Evaluating the recyclability of powders in additive manufacturing has been a long-term challenge.In this study,the microstructure and mechanical properties of a nickel-based superalloy fabricated by laser powder-bed fusion(LPBF)using recycled powders were investigated.Re-melted powder surfaces,satellite particles,and deformed powders were found in the recycled powders,combined with a high-oxygencontent surface layer.The increasing oxygen content led to the formation of high-density oxide inclusions;moreover,printing-induced cracks widely occurred and mainly formed along the grain boundaries in the as-built LPBF nickel-based superalloys fabricated using recycled powders.A little change in the Si or Mn content did not increase the hot cracking susceptibility(HCS)of the printed parts.The changing aspect ratio and the surface damage of the recycled powders might contribute to increasing the crack density.Moreover,the configuration of cracks in the as-built parts led to anisotropic mechanical properties,mainly resulting in extremely low ductility vertical to the building direction,and the cracks mainly propagated along the cellular boundary owing to the existence of a brittle precipitation phase.
基金the National Key Research and Development Program of China(Grant Nos.2017YFB0701603 and 2017YFB0701502).
文摘Heavy elements(X=Ta/W/Re)play an important role in the performance of superalloys,which enhance the strength,anti-oxidation,creep resistance,and anti-corrosiveness of alloy materials in a high-temperature environment.In the present research,the heavy element doping effects in FCC-Ni(γ)and Ni_(3)Al(γ')systems are investigated in terms of their thermodynamic and mechanical properties,as well as electronic structures.The lattice constant,bulk modulus,elastic constant,and dopant formation energy in non-spin,spin polarized,and spin-orbit coupling(SOC)calculations are compared.The results show that the SOC effects are important in accurate electronic structure calculations for alloys with heavy elements.We find that including spin for bothγandγ'phases is necessary and sufficient for most cases,but the dopant formation energy is sensitive to different spin effects,for instance,in the absence of SOC,even spin-polarized calculations give 1%to 9%variance in the dopant formation energy in our model.Electronic structures calculations indicate that spin polarization causes a split in the metal d states,and SOC introduces a variance in the spin-up and spin-down states of the d states of heavy metals and reduces the magnetic moment of the system.