Co-Ni-based superalloys are known for their capability to function at elevated temperatures and superior hot corrosion and thermal fatigue resistance.Therefore,these alloys show potential as crucial high-temperature s...Co-Ni-based superalloys are known for their capability to function at elevated temperatures and superior hot corrosion and thermal fatigue resistance.Therefore,these alloys show potential as crucial high-temperature structural materials for aeroengine and gas turbine hot-end components.Our previous work elucidated the influence of Ti and Ta on the high-temperature mechanical properties of alloys.However,the intricate interaction among elements considerably affects the oxidation resistance of alloys.In this paper,Co-35Ni-10Al-2W-5Cr-2Mo-1Nb-xTi-(5−x)Ta alloys(x=1,2,3,4)with varying Ti and Ta contents were designed and compounded,and their oxidation resistance was investigated at the temperature range from 800 to 1000℃.After oxidation at three test conditions,namely,800℃for 200 h,900℃for 200 h,and 1000℃for 50 h,the main structure of the oxide layer of the alloy consisted of spinel,Cr_(2)O_(3),and Al_(2)O_(3)from outside to inside.Oxides consisting of Ta,W,and Mo formed below the Cr_(2)O_(3)layer.The interaction of Ti and Ta imparted the highest oxidation resistance to 3Ti2Ta alloy.Conversely,an excessive amount of Ti or Ta resulted in an adverse effect on the oxidation resistance of the alloys.This study reports the volatilization of W and Mo oxides during the oxidation process of Co-Ni-based cast superalloys with a high Al content for the first time and explains the formation mechanism of holes in the oxide layer.The results provide a basis for gaining insights into the effects of the interaction of alloying elements on the oxidation resistance of the alloys they form.展开更多
The additive manufacturing(AM)of Ni-based superalloys has attracted extensive interest from both academia and industry due to its unique capabilities to fabricate complex and high-performance components for use in hig...The additive manufacturing(AM)of Ni-based superalloys has attracted extensive interest from both academia and industry due to its unique capabilities to fabricate complex and high-performance components for use in high-end industrial systems.However,the intense temperature gradient induced by the rapid heating and cooling processes of AM can generate high levels of residual stress and metastable chemical and structural states,inevitably leading to severe metallurgical defects in Ni-based superalloys.Cracks are the greatest threat to these materials’integrity as they can rapidly propagate and thereby cause sudden and non-predictable failure.Consequently,there is a need for a deeper understanding of residual stress and cracking mechanisms in additively manufactured Ni-based superalloys and ways to potentially prevent cracking,as this knowledge will enable the wider application of these unique materials.To this end,this paper comprehensively reviews the residual stress and the various mechanisms of crack formation in Ni-based superalloys during AM.In addition,several common methods for inhibiting crack formation are presented to assist the research community to develop methods for the fabrication of crack-free additively manufactured components.展开更多
To enhance the accuracy of mechanical simulation in the directional solidification process of turbine blades for heavy-duty gas turbines,a new constitutive model that employs machine learning methods was developed.Thi...To enhance the accuracy of mechanical simulation in the directional solidification process of turbine blades for heavy-duty gas turbines,a new constitutive model that employs machine learning methods was developed.This model incorporates incremental learning and transfer learning,thus improves the predictive accuracy and generalization performance.To account for the anisotropy of the directionally solidified alloy,a deformation direction parameter is added to the model,enabling prediction of the stress-strain relationship of the alloy under different deformation directions.The predictive capabilities of both models are evaluated using correlation coefficient(R),average relative error(δ),and value of relative error(RE).Compared to the traditional model,the machine learning constitutive model achieves higher prediction accuracy and better generalization performance.This offers a new approach for the establishment of flow constitutive models for other directionally solidified and single-crystal superalloys.展开更多
The slabs of a single crystal superalloy were poured with 2.2% Re, 3.2% Re and 4.2% Re and otherelement contents of the alloys were basicalIy kept no changed. The effects of Re on the ultimatetensile strength, creep r...The slabs of a single crystal superalloy were poured with 2.2% Re, 3.2% Re and 4.2% Re and otherelement contents of the alloys were basicalIy kept no changed. The effects of Re on the ultimatetensile strength, creep rupture life and rafting of a single crystal superalloy were studied. Theresults showed that with increasing Re content the ultimate tensile strength decreased but theplasticity increased at 649℃. and the creep rupture life remarkably increased while the plasticitydecreased at 982℃/248.2 MPa. 1038℃/206.8 MPa and 1070℃/176.8 MPa for the alloy, on themicrostructure aspect, with increasing the creep rupture life of the alloy the rafting was gettingbigger and bigger at the same test condition, and the rafting suppressed creep and increasedcreep rupture life in this single crystal superalloy.展开更多
An anisotropic micromechanics model based on the equivalent inclusion method is developed to investigate the rafting direction of Ni-based single crystal superalloys.The micromechanical model considers actual cubic st...An anisotropic micromechanics model based on the equivalent inclusion method is developed to investigate the rafting direction of Ni-based single crystal superalloys.The micromechanical model considers actual cubic structure and orthogonal anisotropy properties. The von Mises stress,elastic strain energy density, and hydrostatic pressure in different inclusions of micromechanical model are calculated when applying a tensile or compressive loading along the[001] direction. The calculated results can successfully predict the rafting direction for alloys exhibiting a positive or a negative mismatch, which are in agreement with pervious experimental and theoretical studies. Moreover, the elastic constant differences and mismatch degree of the matrix and precipitate phases and their influences on the rafting direction are carefully discussed.展开更多
To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni–Co–Fe-based end-of-life(EoL) superalloys, knowledge of their activity coefficien...To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni–Co–Fe-based end-of-life(EoL) superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coefficients of NiO and CoO in CaO–Al_2O_3–SiO_2 slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO–Al_2O_3–SiO_2 slag. The activity coefficients of NiO and CoO in CaO–Al_2O_3–SiO_2 slag both show a positive deviation from Raoult's law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B =(%CaO)/(%SiO_2) = 1, where B is the basicity. We observed that controlling the slag composition at approximately B = 1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.展开更多
Unlike the reported leaching technologies of waste superalloys, the process of the “atomized spray-sulfuric acid leaching nickel and cobalt” technology was put forward in the present work according to the compositio...Unlike the reported leaching technologies of waste superalloys, the process of the “atomized spray-sulfuric acid leaching nickel and cobalt” technology was put forward in the present work according to the compositions of waste superalloys. The effects of sulfuric acid temperature, concentration, leaching time, stirring speed and size of superalloys on leaching of Ni and Co from waste superalloys have been mainly investigated, and the optimum leaching conditions were determined and reported. The leaching rates for nickel and cobalt were 96.68% and 96.63%, respectively, and the contents of nickel and cobalt in leaching slag were 6.77% and 0.96%, respectively. The obtained leaching solution containing Ni and Co could be used for production of Ni and Co products after removal.展开更多
This paper presents hot corrosion results carried out systematically on the selected nickel based superalloys such as IN 738 LC, GTM-SU-718 and GTM-SU-263 for marine gas turbine engines both at high and low temperatur...This paper presents hot corrosion results carried out systematically on the selected nickel based superalloys such as IN 738 LC, GTM-SU-718 and GTM-SU-263 for marine gas turbine engines both at high and low temperatures that represent type I and type II hot corrosion respectively. The results were compared with advanced superalloy under similar conditions in order to understand the characteristics of the selected superalloys. It is observed that the selected superalloys are relatively more resistant to type I and type II hot corrosion when compared to advanced superalloy. In fact, the advanced superalloy is extremely vulnerable to both types of hot corrosion. Subsequently, the relevant reaction mechanisms that are responsible for slow and faster degradation of various superalloys under varied hot corrosion conditions were discussed. Based on the results obtained with different techniques, a degradation mechanism for all the selected superalloys as well as advanced superalloy under both types of hot corrosion conditions was explained. Finally, the necessity as well as developmental efforts with regard to smart corrosion resistant coatings for their effective protection under high temperature conditions was stressed for their enhanced efficiency.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 doping effects on the stacking fault energies(SFEs),including the superlattice intrinsic stacking fault and superlattice extrinsic stacking fault,were studied by first principles calculation of the γ' phase i...The doping effects on the stacking fault energies(SFEs),including the superlattice intrinsic stacking fault and superlattice extrinsic stacking fault,were studied by first principles calculation of the γ' phase in the Ni-based superalloys.The formation energy results show that the main alloying elements in Ni-based superalloys,such as Re,Cr,Mo,Ta,and W,prefer to occupy the Al-site in Ni3Al,Co shows a weak tendency to occupy the Ni-site,and Ru shows a weak tendency to occupy the Al-site.The SFE results show that Co and Ru could decrease the SFEs when added to fault planes,while other main elements increase SFEs.The double-packed superlattice intrinsic stacking fault energies are lower than superlattice extrinsic stacking fault energies when elements(except Co)occupy an Al-site.Furthermore,the SFEs show a symmetrical distribution with the location of the elements in the ternary model.A detailed electronic structure analysis of the Ru effects shows that SFEs correlated with not only the symmetry reduction of the charge accumulation but also the changes in structural energy.展开更多
The phase partition and site preference of Re atoms in a ternary Ni-Al-Re model alloy,including the electronic structure of different Re configurations,are investigated with first-principles calculations and atom prob...The phase partition and site preference of Re atoms in a ternary Ni-Al-Re model alloy,including the electronic structure of different Re configurations,are investigated with first-principles calculations and atom probe tomography.The Re distribution of single,nearest neighbor(NN),next-nearest neighbor(NNN),and cluster configurations are respectively designed in the models withγandγphases.The results show that the Re atoms tend to enteringγphase and the Re atoms prefer to occupy the Al sites inγphase.The Re cluster with a combination of NN and NNN Re-Re pair configuration is not preferred than the isolated Re atom in the Ni-based superalloys,and the configuration with isolated Re atom is more preferred in the system.Especially,the electronic states are analyzed and the energetic parameters are calculated.The electronic structure analyses show there exists strong Ni-Re electronic interaction and it is mainly contributed by the d-d hybridization.The characteristic features of the electronic states of the Re doping effects are also given.It is also found that Re atoms prefer the Al sites inγside at the interface.The density of states at or near the Fermi level and the d-d hybridizations of NN Ni-Re are found to be important in the systems.展开更多
NiCo-based superalloys exhibit higher strength and creep resistance over conventional superalloys.Compositional effects on elastic properties of the γ and γ' phases in newly-developed NiCo-based superalloys were...NiCo-based superalloys exhibit higher strength and creep resistance over conventional superalloys.Compositional effects on elastic properties of the γ and γ' phases in newly-developed NiCo-based superalloys were investigated by first-principles calculation combined with special quasi-random structures.The lattice constant,bulk modulus,and elastic constants vary linearly with the Co concentration in the NiCo solution.In the selected(Ni,Co)3(Al,W)and(Ni,Co)3(Al,Ti)model γ' phase,the lattice constant,and bulk modulus show a linear trend with alloying element concentrations.The addition of Co,Ti,and W can regulate lattice mismatch and increase the bulk modulus,simultaneously.W-addition shows excellent performance in strengthening the elastic properties in the γ' phase.Systems become unstable with higher W and Ni contents,e.g.,(Ni0.75Co0.25)3(Al0.25 W0.75),and become brittle with higher W and Co addition,e.g.,Co3(Al0.25 W0.75).Furthermore,Co,Ti,and W can increase the elastic constants on the whole,and such high elastic constants always correspond to a high elastic modulus.The anisotropy index always corresponds to the nature of Young's modulus in a specific direction.展开更多
On the basis of an investigation on σ phase inNi-base cast superalloy K24 and the results aboutσ phase in other Ni-base superalloys,an embrittl-ing mechanism and a softening mechanism,bywhich platelike σ phase weak...On the basis of an investigation on σ phase inNi-base cast superalloy K24 and the results aboutσ phase in other Ni-base superalloys,an embrittl-ing mechanism and a softening mechanism,bywhich platelike σ phase weakens the Ni-basesuperalloys,have been proposed.It is consideredthat the platelike morphology and the habit precipi-tation along{111}of σ phase are necessary condi-tions for both mechanisms.The embrittling mecha-nism is dominant at room temperature and highstrain rate,and the softening mechanism is domi-nant at high temperature and low strain rate.Ac-cording to the idea of the softening mechanism andthe analyses of σ phase and alloy compositions,it isconsidered that Nb,Mo and W in the alloys may beresistant to the detrimental effect of σ phase on thestress-rupture properties of the alloys.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
The strengthening effects of alloying elements Re,Ta,and W in the[110](001)dislocation core of theγ/γ'interface are studied by first-principles calculations.From the level of energy the substitution formation en...The strengthening effects of alloying elements Re,Ta,and W in the[110](001)dislocation core of theγ/γ'interface are studied by first-principles calculations.From the level of energy the substitution formation energies and the migration energies of alloying elements are computed and from the level of electron the differential charge density(DCD)and the partial density of states(PDOSs)are computed.Alloying elements above are found to tend to substitute for Al sitesγ'phase by analyzing the substitution formation energy.The calculation results for the migration energies of alloying elements indicate that the stability of the[110](001)dislocation core is enhanced by adding Ta,W,and Re and the strengthening effect of Re is the strongest.Our results agree with the relevant experiments.The electronic structure analysis indicates that the electronic interaction between Re-nearest neighbor(NN)Ni is the strongest.The reason why the doped atoms have different strengthening effects in the[110](001)dislocation core is explained at the level of electron.展开更多
In order to investigate the elastic properties of directionally solidified(DS)superalloys,an elasticity model called boundaries elastic model(GBE model),considering grain boundaries and tensile orientations,is propose...In order to investigate the elastic properties of directionally solidified(DS)superalloys,an elasticity model called boundaries elastic model(GBE model),considering grain boundaries and tensile orientations,is proposed in this paper.Two assumptions are adopted in the GBE model:(1)The displacement of grains,which moves along the perpendicular direction,is restricted by the grain boundaries;(2)Grain boundaries influence region(GBIR)is formed around the grain boundaries.Based on the single crystal(SC)calculation method of elastic properties,the GBE model can well predict macroscopic equivalent elastic modulus(Young’s modulus)of DS superalloys under different tensile orientations effectively.To demonstrate the correctness of the GBE model,3D finite element simulation is adopted and tensile experiments on a Ni3Al?base DS superalloy(IC10)along five tensile orientations are carried out.Meanwhile,the grain boundaries are observed by light microscopy and transmission electron microscope(TEM).Therefore,the GBE model is proved to be feasible by comparing the simulated results with the experiments.展开更多
Solid-solution strengthened superalloys are widely used because they possess excellent levels of high temperature strength and environmental resistance in combination with ease of fabrication.This latter factor is of ...Solid-solution strengthened superalloys are widely used because they possess excellent levels of high temperature strength and environmental resistance in combination with ease of fabrication.This latter factor is of utmost importance since it is a primary economic determinant.From a metal producer’s point of view,it determines the viable range of product forms that can be offered to the marketplace.From a user’s point of view,it determines the viable range of manufacturing processes that can be used to make the final product.For both the producer and user,an alloy’s heat treatment and property response is a central issue for defining fabricability.The areas of interest are typically quite fundamental and include such phenomena as recrystallization and grain growth,critical strain effects,relief of residual stresses,and cooling rate effects.In heat resisting alloys,these phenomena often involve subtle complexities due to the precipitation of carbides and,in some cases,the precipitation of intermetallic phases. This paper will deal with these complexities,providing relevant data and concrete examples wherever possible.The information presented should enable the proper selection of heat treatment practices for solid-solution strengthened superalloys.展开更多
Fracture toughness plays a vital role in damage tolerance design of materials and assessment of structural integrity.To solve these problems of com-plexity,time-consuming,and low accuracy in obtaining the fracture tou...Fracture toughness plays a vital role in damage tolerance design of materials and assessment of structural integrity.To solve these problems of com-plexity,time-consuming,and low accuracy in obtaining the fracture toughness value of nickel-based superalloys through experiments.A combination prediction model is proposed based on the principle of materials genome engineering,the fracture toughness values of nickel-based superalloys at different temperatures,and different compositions can be predicted based on the existing experimental data.First,to solve the problem of insufficient feature extraction based on manual experience,the Deep Belief Network(DBN)is used to extract features,and an attention mechanism module is introduced.To achieve the purpose of strengthen-ing the important features,an attention weight is assigned to each feature accord-ing to the importance of the feature.Then,the feature vectors obtained by the DBN module based on the Attention mechanism(A-DBN)are spliced with the original features.Thus,the prediction accuracy of the model is improved by extracting high-order combined features and low-order linear features between input and output data.Finally,the spliced feature vectors are put into the Support Vector Regression(SVR)model to further improve the regression prediction abil-ity of the model.The results of the contrast experiment show that the model can effectively improve the prediction accuracy of the fracture toughness value of nickel-based superalloys.展开更多
The hot-corrosion resistant superalloys have been widely applied in the gas turbines for power generation industry,the marine gas turbines in the aircraft carrier and missile destroyer as well as the aeroengines in sh...The hot-corrosion resistant superalloys have been widely applied in the gas turbines for power generation industry,the marine gas turbines in the aircraft carrier and missile destroyer as well as the aeroengines in shipboard aircraft and offshore fighter plane.Based on the ten kinds of hot-corrosion superalloys that were developed by the authors in the recent 10 years,the paper has reviewed the status and development of hot-corrosion resistant superalloys in domestic and overseas.The characteristics of chemical composition, microstructure,mechanical properties and manufacturing process are analyzed emphatically.Simultaneously the applications of hot-corrosion resistant superalloys are introduced as well.展开更多
基金the National Major Science and Technology Projects of China(Nos.J2019-VII-0010-0150 and J2019-VI-0009-0123)National Natural Science Foundation of China(Nos.52022011 and 52090041)+3 种基金Beijing Nova Program(No.Z211100002121170)Science Center for Gas Turbine Project(No.P2021-A-IV-001-002)Science and Technology on Advanced High Temperature Structural Materials Laboratory(No.6142903210306)Xiaomi Young Scholars Program.
文摘Co-Ni-based superalloys are known for their capability to function at elevated temperatures and superior hot corrosion and thermal fatigue resistance.Therefore,these alloys show potential as crucial high-temperature structural materials for aeroengine and gas turbine hot-end components.Our previous work elucidated the influence of Ti and Ta on the high-temperature mechanical properties of alloys.However,the intricate interaction among elements considerably affects the oxidation resistance of alloys.In this paper,Co-35Ni-10Al-2W-5Cr-2Mo-1Nb-xTi-(5−x)Ta alloys(x=1,2,3,4)with varying Ti and Ta contents were designed and compounded,and their oxidation resistance was investigated at the temperature range from 800 to 1000℃.After oxidation at three test conditions,namely,800℃for 200 h,900℃for 200 h,and 1000℃for 50 h,the main structure of the oxide layer of the alloy consisted of spinel,Cr_(2)O_(3),and Al_(2)O_(3)from outside to inside.Oxides consisting of Ta,W,and Mo formed below the Cr_(2)O_(3)layer.The interaction of Ti and Ta imparted the highest oxidation resistance to 3Ti2Ta alloy.Conversely,an excessive amount of Ti or Ta resulted in an adverse effect on the oxidation resistance of the alloys.This study reports the volatilization of W and Mo oxides during the oxidation process of Co-Ni-based cast superalloys with a high Al content for the first time and explains the formation mechanism of holes in the oxide layer.The results provide a basis for gaining insights into the effects of the interaction of alloying elements on the oxidation resistance of the alloys they form.
基金This work was supported by Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shenzhen Park Project:HZQB-KCZYB-2020030the National Natural Science Foundation of China(No.91860131and No.52074157)+2 种基金Guangdong Provincial Department of Science and Technology,Key-Area Research and Development Program of Guangdong Province(No.2020B090923002)the National Key Research and Development Program of China(No.2017YFB0702901)the Shenzhen Science and Technology Innovation Commission(No.JCYJ20170817111811303,No.KQTD20170328154443162and No.ZDSYS201703031748354).
文摘The additive manufacturing(AM)of Ni-based superalloys has attracted extensive interest from both academia and industry due to its unique capabilities to fabricate complex and high-performance components for use in high-end industrial systems.However,the intense temperature gradient induced by the rapid heating and cooling processes of AM can generate high levels of residual stress and metastable chemical and structural states,inevitably leading to severe metallurgical defects in Ni-based superalloys.Cracks are the greatest threat to these materials’integrity as they can rapidly propagate and thereby cause sudden and non-predictable failure.Consequently,there is a need for a deeper understanding of residual stress and cracking mechanisms in additively manufactured Ni-based superalloys and ways to potentially prevent cracking,as this knowledge will enable the wider application of these unique materials.To this end,this paper comprehensively reviews the residual stress and the various mechanisms of crack formation in Ni-based superalloys during AM.In addition,several common methods for inhibiting crack formation are presented to assist the research community to develop methods for the fabrication of crack-free additively manufactured components.
基金supported by the National Science and Technology Major Project(2017-VII-0008-0101).
文摘To enhance the accuracy of mechanical simulation in the directional solidification process of turbine blades for heavy-duty gas turbines,a new constitutive model that employs machine learning methods was developed.This model incorporates incremental learning and transfer learning,thus improves the predictive accuracy and generalization performance.To account for the anisotropy of the directionally solidified alloy,a deformation direction parameter is added to the model,enabling prediction of the stress-strain relationship of the alloy under different deformation directions.The predictive capabilities of both models are evaluated using correlation coefficient(R),average relative error(δ),and value of relative error(RE).Compared to the traditional model,the machine learning constitutive model achieves higher prediction accuracy and better generalization performance.This offers a new approach for the establishment of flow constitutive models for other directionally solidified and single-crystal superalloys.
文摘The slabs of a single crystal superalloy were poured with 2.2% Re, 3.2% Re and 4.2% Re and otherelement contents of the alloys were basicalIy kept no changed. The effects of Re on the ultimatetensile strength, creep rupture life and rafting of a single crystal superalloy were studied. Theresults showed that with increasing Re content the ultimate tensile strength decreased but theplasticity increased at 649℃. and the creep rupture life remarkably increased while the plasticitydecreased at 982℃/248.2 MPa. 1038℃/206.8 MPa and 1070℃/176.8 MPa for the alloy, on themicrostructure aspect, with increasing the creep rupture life of the alloy the rafting was gettingbigger and bigger at the same test condition, and the rafting suppressed creep and increasedcreep rupture life in this single crystal superalloy.
基金supported by The National Natural Science Foundation of China (Grants 11102139 and 11472195)The Natural Science Foundation of Hubei Province of China (Grant 2014CFB713)
文摘An anisotropic micromechanics model based on the equivalent inclusion method is developed to investigate the rafting direction of Ni-based single crystal superalloys.The micromechanical model considers actual cubic structure and orthogonal anisotropy properties. The von Mises stress,elastic strain energy density, and hydrostatic pressure in different inclusions of micromechanical model are calculated when applying a tensile or compressive loading along the[001] direction. The calculated results can successfully predict the rafting direction for alloys exhibiting a positive or a negative mismatch, which are in agreement with pervious experimental and theoretical studies. Moreover, the elastic constant differences and mismatch degree of the matrix and precipitate phases and their influences on the rafting direction are carefully discussed.
基金the support of a scholarship provided by the Japan Society for the Promotion of Science(No. H26-3293)the scholarship provided by the Ministry of Education,Culture,Sports,Science and Technology,Japan(Registered number: 123032) during his doctor course
文摘To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni–Co–Fe-based end-of-life(EoL) superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coefficients of NiO and CoO in CaO–Al_2O_3–SiO_2 slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO–Al_2O_3–SiO_2 slag. The activity coefficients of NiO and CoO in CaO–Al_2O_3–SiO_2 slag both show a positive deviation from Raoult's law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B =(%CaO)/(%SiO_2) = 1, where B is the basicity. We observed that controlling the slag composition at approximately B = 1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.
文摘Unlike the reported leaching technologies of waste superalloys, the process of the “atomized spray-sulfuric acid leaching nickel and cobalt” technology was put forward in the present work according to the compositions of waste superalloys. The effects of sulfuric acid temperature, concentration, leaching time, stirring speed and size of superalloys on leaching of Ni and Co from waste superalloys have been mainly investigated, and the optimum leaching conditions were determined and reported. The leaching rates for nickel and cobalt were 96.68% and 96.63%, respectively, and the contents of nickel and cobalt in leaching slag were 6.77% and 0.96%, respectively. The obtained leaching solution containing Ni and Co could be used for production of Ni and Co products after removal.
文摘This paper presents hot corrosion results carried out systematically on the selected nickel based superalloys such as IN 738 LC, GTM-SU-718 and GTM-SU-263 for marine gas turbine engines both at high and low temperatures that represent type I and type II hot corrosion respectively. The results were compared with advanced superalloy under similar conditions in order to understand the characteristics of the selected superalloys. It is observed that the selected superalloys are relatively more resistant to type I and type II hot corrosion when compared to advanced superalloy. In fact, the advanced superalloy is extremely vulnerable to both types of hot corrosion. Subsequently, the relevant reaction mechanisms that are responsible for slow and faster degradation of various superalloys under varied hot corrosion conditions were discussed. Based on the results obtained with different techniques, a degradation mechanism for all the selected superalloys as well as advanced superalloy under both types of hot corrosion conditions was explained. Finally, the necessity as well as developmental efforts with regard to smart corrosion resistant coatings for their effective protection under high temperature conditions was stressed for their enhanced efficiency.
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 the National Key Research and Development Program of China(Grant No.2017YFB0701502).
文摘The doping effects on the stacking fault energies(SFEs),including the superlattice intrinsic stacking fault and superlattice extrinsic stacking fault,were studied by first principles calculation of the γ' phase in the Ni-based superalloys.The formation energy results show that the main alloying elements in Ni-based superalloys,such as Re,Cr,Mo,Ta,and W,prefer to occupy the Al-site in Ni3Al,Co shows a weak tendency to occupy the Ni-site,and Ru shows a weak tendency to occupy the Al-site.The SFE results show that Co and Ru could decrease the SFEs when added to fault planes,while other main elements increase SFEs.The double-packed superlattice intrinsic stacking fault energies are lower than superlattice extrinsic stacking fault energies when elements(except Co)occupy an Al-site.Furthermore,the SFEs show a symmetrical distribution with the location of the elements in the ternary model.A detailed electronic structure analysis of the Ru effects shows that SFEs correlated with not only the symmetry reduction of the charge accumulation but also the changes in structural energy.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0701503)。
文摘The phase partition and site preference of Re atoms in a ternary Ni-Al-Re model alloy,including the electronic structure of different Re configurations,are investigated with first-principles calculations and atom probe tomography.The Re distribution of single,nearest neighbor(NN),next-nearest neighbor(NNN),and cluster configurations are respectively designed in the models withγandγphases.The results show that the Re atoms tend to enteringγphase and the Re atoms prefer to occupy the Al sites inγphase.The Re cluster with a combination of NN and NNN Re-Re pair configuration is not preferred than the isolated Re atom in the Ni-based superalloys,and the configuration with isolated Re atom is more preferred in the system.Especially,the electronic states are analyzed and the energetic parameters are calculated.The electronic structure analyses show there exists strong Ni-Re electronic interaction and it is mainly contributed by the d-d hybridization.The characteristic features of the electronic states of the Re doping effects are also given.It is also found that Re atoms prefer the Al sites inγside at the interface.The density of states at or near the Fermi level and the d-d hybridizations of NN Ni-Re are found to be important in the systems.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0701502).
文摘NiCo-based superalloys exhibit higher strength and creep resistance over conventional superalloys.Compositional effects on elastic properties of the γ and γ' phases in newly-developed NiCo-based superalloys were investigated by first-principles calculation combined with special quasi-random structures.The lattice constant,bulk modulus,and elastic constants vary linearly with the Co concentration in the NiCo solution.In the selected(Ni,Co)3(Al,W)and(Ni,Co)3(Al,Ti)model γ' phase,the lattice constant,and bulk modulus show a linear trend with alloying element concentrations.The addition of Co,Ti,and W can regulate lattice mismatch and increase the bulk modulus,simultaneously.W-addition shows excellent performance in strengthening the elastic properties in the γ' phase.Systems become unstable with higher W and Ni contents,e.g.,(Ni0.75Co0.25)3(Al0.25 W0.75),and become brittle with higher W and Co addition,e.g.,Co3(Al0.25 W0.75).Furthermore,Co,Ti,and W can increase the elastic constants on the whole,and such high elastic constants always correspond to a high elastic modulus.The anisotropy index always corresponds to the nature of Young's modulus in a specific direction.
文摘On the basis of an investigation on σ phase inNi-base cast superalloy K24 and the results aboutσ phase in other Ni-base superalloys,an embrittl-ing mechanism and a softening mechanism,bywhich platelike σ phase weakens the Ni-basesuperalloys,have been proposed.It is consideredthat the platelike morphology and the habit precipi-tation along{111}of σ phase are necessary condi-tions for both mechanisms.The embrittling mecha-nism is dominant at room temperature and highstrain rate,and the softening mechanism is domi-nant at high temperature and low strain rate.Ac-cording to the idea of the softening mechanism andthe analyses of σ phase and alloy compositions,it isconsidered that Nb,Mo and W in the alloys may beresistant to the detrimental effect of σ phase on thestress-rupture properties of the alloys.
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.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFB0701503).
文摘The strengthening effects of alloying elements Re,Ta,and W in the[110](001)dislocation core of theγ/γ'interface are studied by first-principles calculations.From the level of energy the substitution formation energies and the migration energies of alloying elements are computed and from the level of electron the differential charge density(DCD)and the partial density of states(PDOSs)are computed.Alloying elements above are found to tend to substitute for Al sitesγ'phase by analyzing the substitution formation energy.The calculation results for the migration energies of alloying elements indicate that the stability of the[110](001)dislocation core is enhanced by adding Ta,W,and Re and the strengthening effect of Re is the strongest.Our results agree with the relevant experiments.The electronic structure analysis indicates that the electronic interaction between Re-nearest neighbor(NN)Ni is the strongest.The reason why the doped atoms have different strengthening effects in the[110](001)dislocation core is explained at the level of electron.
基金supported by the National Natural Science Foundation of China (No.51205190)the Fundamental Research Funds for the Central Universities (No.NS2016026)+1 种基金the Aeronautical Power Science Fund Project (No. 6141B090317)the Innovation Fund of Jiangsu Province, China (No.KYLX-0304)
文摘In order to investigate the elastic properties of directionally solidified(DS)superalloys,an elasticity model called boundaries elastic model(GBE model),considering grain boundaries and tensile orientations,is proposed in this paper.Two assumptions are adopted in the GBE model:(1)The displacement of grains,which moves along the perpendicular direction,is restricted by the grain boundaries;(2)Grain boundaries influence region(GBIR)is formed around the grain boundaries.Based on the single crystal(SC)calculation method of elastic properties,the GBE model can well predict macroscopic equivalent elastic modulus(Young’s modulus)of DS superalloys under different tensile orientations effectively.To demonstrate the correctness of the GBE model,3D finite element simulation is adopted and tensile experiments on a Ni3Al?base DS superalloy(IC10)along five tensile orientations are carried out.Meanwhile,the grain boundaries are observed by light microscopy and transmission electron microscope(TEM).Therefore,the GBE model is proved to be feasible by comparing the simulated results with the experiments.
文摘Solid-solution strengthened superalloys are widely used because they possess excellent levels of high temperature strength and environmental resistance in combination with ease of fabrication.This latter factor is of utmost importance since it is a primary economic determinant.From a metal producer’s point of view,it determines the viable range of product forms that can be offered to the marketplace.From a user’s point of view,it determines the viable range of manufacturing processes that can be used to make the final product.For both the producer and user,an alloy’s heat treatment and property response is a central issue for defining fabricability.The areas of interest are typically quite fundamental and include such phenomena as recrystallization and grain growth,critical strain effects,relief of residual stresses,and cooling rate effects.In heat resisting alloys,these phenomena often involve subtle complexities due to the precipitation of carbides and,in some cases,the precipitation of intermetallic phases. This paper will deal with these complexities,providing relevant data and concrete examples wherever possible.The information presented should enable the proper selection of heat treatment practices for solid-solution strengthened superalloys.
基金supported by Beijing Advanced Innovation Center for Materials Genome Engineering,Beijing Information Science and Technology University,Beijing Key Laboratory of Internet Culture and Digital Dissemination Research(No.ICDDXN004).
文摘Fracture toughness plays a vital role in damage tolerance design of materials and assessment of structural integrity.To solve these problems of com-plexity,time-consuming,and low accuracy in obtaining the fracture toughness value of nickel-based superalloys through experiments.A combination prediction model is proposed based on the principle of materials genome engineering,the fracture toughness values of nickel-based superalloys at different temperatures,and different compositions can be predicted based on the existing experimental data.First,to solve the problem of insufficient feature extraction based on manual experience,the Deep Belief Network(DBN)is used to extract features,and an attention mechanism module is introduced.To achieve the purpose of strengthen-ing the important features,an attention weight is assigned to each feature accord-ing to the importance of the feature.Then,the feature vectors obtained by the DBN module based on the Attention mechanism(A-DBN)are spliced with the original features.Thus,the prediction accuracy of the model is improved by extracting high-order combined features and low-order linear features between input and output data.Finally,the spliced feature vectors are put into the Support Vector Regression(SVR)model to further improve the regression prediction abil-ity of the model.The results of the contrast experiment show that the model can effectively improve the prediction accuracy of the fracture toughness value of nickel-based superalloys.
文摘The hot-corrosion resistant superalloys have been widely applied in the gas turbines for power generation industry,the marine gas turbines in the aircraft carrier and missile destroyer as well as the aeroengines in shipboard aircraft and offshore fighter plane.Based on the ten kinds of hot-corrosion superalloys that were developed by the authors in the recent 10 years,the paper has reviewed the status and development of hot-corrosion resistant superalloys in domestic and overseas.The characteristics of chemical composition, microstructure,mechanical properties and manufacturing process are analyzed emphatically.Simultaneously the applications of hot-corrosion resistant superalloys are introduced as well.
