Vacuum diffusion bonding of a TiAl based alloy (TAD) to a titanium alloy (TC2) was carried out at 1 273 K for 15～120 min under a pressure of 25 MPa . The kinds of the reaction products and the interface s...Vacuum diffusion bonding of a TiAl based alloy (TAD) to a titanium alloy (TC2) was carried out at 1 273 K for 15～120 min under a pressure of 25 MPa . The kinds of the reaction products and the interface structures of the joints were investigated by SEM, EPMA and XRD. Based on this, a formation mechanism of the interface structure was elucidated. Experimental and analytical results show that two reaction layers have formed during the diffusion bonding of TAD to TC2. One is Al rich α(Ti)layer adjacent to TC2,and the other is (Ti 3Al+TiAl)layer adjacent to TAD,thus the interface structure of the TAD/TC2 joints is TAD/(Ti 3Al+TiAl)/α(Ti)/TC2.This interface structure forms according to a three stage mechanism,namely(a)the occurrence of a single phase α(Ti)layer;(b)the occurrence of a duplex phase(Ti 3Al+TiAl)layer;and(c)the growth of the α(Ti)and (Ti 3Al+TiAl)layers.展开更多
The ceramic filter in continuous casting tundish can effectively improve the cleanliness of high-performance steel by regulating tundish flow field to promote the removal of inclusions and adsorbing or blocking fine i...The ceramic filter in continuous casting tundish can effectively improve the cleanliness of high-performance steel by regulating tundish flow field to promote the removal of inclusions and adsorbing or blocking fine inclusions in the molten steel into the mold.The interaction between microporous magnesia refractories used as tundish filter and molten interstitial-free(IF)steel at 1873 K was investigated to reveal the formation mechanism of their interface layer and its effect on steel cleanliness by laboratory research and thermodynamic calculations.The results show that the magnesium–aluminum spinel layer at the interface between the molten IF steel and the microporous magnesia refractories is formed mainly by the reaction of MgO in the refractory with the[Al]and[O]in the molten steel,significantly reducing the total O content,the size and amount of inclusions of the molten steel.In addition,the interparticle phases of microporous magnesia refractories at high temperature can adsorb Al_(2)O_(3) and TiO_(2) inclusions in the molten steel into interparticle channels of the refractories to form high melting point spinel,impeding the further penetration of the molten steel.As a result,the consecutive interface layer of high melting point spinel between microporous magnesia refractories and molten steel can improve the cleanliness of the molten steel by adsorbing inclusions in the molten steel and avoid the direct dissolution of refractories of the tundish ceramic filter immersed in the molten steel,increasing their service life.展开更多
The objective of this experimental study is to improve the cementing bond quality of sandstone oil-gas well along the wellbore cement-formation interface(WCFI),so as to ensure long-term zonal isolation throughout the ...The objective of this experimental study is to improve the cementing bond quality of sandstone oil-gas well along the wellbore cement-formation interface(WCFI),so as to ensure long-term zonal isolation throughout the lifecycle of the well by using NsO solution as filtercake modifier which was developed in the laboratory.According to designed experimental method and API RP 10,the effectiveness of filtercake modifier(NSO)on the bonding strength at the WCFI was assessed by using designed simulated wellbore as sandstone formation.The experimental results indicated that the samples which were treated with NsO solution had higher bond strength over untreated samples.The strength generally increased with curing period as for treated samples,0.198,0.374,0.433 and 0.473 MPa for 3,7,15,and 30 days respectively while for the untreated samples the bond strength were 0.050,0.070,0.81 and 0.100 MPa for the same period.The water-based filtercake modification techniques had significantly enhanced the bonding strength of WCFI by increasing rates above 296%.Improvement of bond strength to the treated sample was due to filtercake modification as a result of formation of cementitious material as revealed in FTIR spectral such as Calcium-Silicate-Hydrate(C-S-H)and other geopolymers like Calcium-Aluminium-Silicate-Hydrate(C-A-S-H)and Sodium-Aluminium-Silicate-Hydrate(N-A-S-H)along the interface which filled the existed pores hence reducing porosity hence high strength of bond.The low transmittance value for the NsO treated samples revealed that there were more cementitious materials existing at the WCFI which led to improvement of bonding strength as compared to the untreated samples.The lower/poor bond strength for the untreated samples is due to existence of untreated,thick water-based filtercake films at WCFI,which prevented the complete hydration process between rock grains and cement slurry components to make chemical binder of cement slurry material and formation.2022 The Authors.Publishing services provided by Elsevier B.V.on b展开更多
Unconventional hydrocarbon reservoirs in layered formations,such as tight sandstones and shales,are continually being developed.Hydraulic fracturing is a critical technology for the high-efficiency development of hydr...Unconventional hydrocarbon reservoirs in layered formations,such as tight sandstones and shales,are continually being developed.Hydraulic fracturing is a critical technology for the high-efficiency development of hydrocarbon reservoirs.Understanding the stress field and stability of the formation interface is vital to understanding stress propagation,preferably before the growing hydraulic fracture contacts the formation interface.In this study,models are developed for computing the stress field of hydraulic fracture propagation near the formation interface,and the stress fields within and at the two sides of the formation interface are analyzed.Four failure modes of the interface under the impact of hydraulic fracture propagation in its vicinity are identified,and the corresponding failure criteria are proposed.By simulating the magnitude and direction of peak stress at different parameters,the failure mode and stability of the formation interface are analyzed.Results reveal that when the interface strength is weak,the formation interface fails before the growing hydraulic fracture contacts it,and its stability is significantly related to a variety of factors,including the type of formation interface,rock mechanical properties,far-field stress,structural parameters,distance between the hydraulic fracture and formation interface,and fracturing execution parameters.展开更多
文摘Vacuum diffusion bonding of a TiAl based alloy (TAD) to a titanium alloy (TC2) was carried out at 1 273 K for 15～120 min under a pressure of 25 MPa . The kinds of the reaction products and the interface structures of the joints were investigated by SEM, EPMA and XRD. Based on this, a formation mechanism of the interface structure was elucidated. Experimental and analytical results show that two reaction layers have formed during the diffusion bonding of TAD to TC2. One is Al rich α(Ti)layer adjacent to TC2,and the other is (Ti 3Al+TiAl)layer adjacent to TAD,thus the interface structure of the TAD/TC2 joints is TAD/(Ti 3Al+TiAl)/α(Ti)/TC2.This interface structure forms according to a three stage mechanism,namely(a)the occurrence of a single phase α(Ti)layer;(b)the occurrence of a duplex phase(Ti 3Al+TiAl)layer;and(c)the growth of the α(Ti)and (Ti 3Al+TiAl)layers.
基金The authors are grateful to the National Natural Science Foundation of China(Nos.U1860205 and 52174323)Innovation Team Cultivation Funding Project of Wuhan University of Science and Technology(2018TDX08).
文摘The ceramic filter in continuous casting tundish can effectively improve the cleanliness of high-performance steel by regulating tundish flow field to promote the removal of inclusions and adsorbing or blocking fine inclusions in the molten steel into the mold.The interaction between microporous magnesia refractories used as tundish filter and molten interstitial-free(IF)steel at 1873 K was investigated to reveal the formation mechanism of their interface layer and its effect on steel cleanliness by laboratory research and thermodynamic calculations.The results show that the magnesium–aluminum spinel layer at the interface between the molten IF steel and the microporous magnesia refractories is formed mainly by the reaction of MgO in the refractory with the[Al]and[O]in the molten steel,significantly reducing the total O content,the size and amount of inclusions of the molten steel.In addition,the interparticle phases of microporous magnesia refractories at high temperature can adsorb Al_(2)O_(3) and TiO_(2) inclusions in the molten steel into interparticle channels of the refractories to form high melting point spinel,impeding the further penetration of the molten steel.As a result,the consecutive interface layer of high melting point spinel between microporous magnesia refractories and molten steel can improve the cleanliness of the molten steel by adsorbing inclusions in the molten steel and avoid the direct dissolution of refractories of the tundish ceramic filter immersed in the molten steel,increasing their service life.
文摘The objective of this experimental study is to improve the cementing bond quality of sandstone oil-gas well along the wellbore cement-formation interface(WCFI),so as to ensure long-term zonal isolation throughout the lifecycle of the well by using NsO solution as filtercake modifier which was developed in the laboratory.According to designed experimental method and API RP 10,the effectiveness of filtercake modifier(NSO)on the bonding strength at the WCFI was assessed by using designed simulated wellbore as sandstone formation.The experimental results indicated that the samples which were treated with NsO solution had higher bond strength over untreated samples.The strength generally increased with curing period as for treated samples,0.198,0.374,0.433 and 0.473 MPa for 3,7,15,and 30 days respectively while for the untreated samples the bond strength were 0.050,0.070,0.81 and 0.100 MPa for the same period.The water-based filtercake modification techniques had significantly enhanced the bonding strength of WCFI by increasing rates above 296%.Improvement of bond strength to the treated sample was due to filtercake modification as a result of formation of cementitious material as revealed in FTIR spectral such as Calcium-Silicate-Hydrate(C-S-H)and other geopolymers like Calcium-Aluminium-Silicate-Hydrate(C-A-S-H)and Sodium-Aluminium-Silicate-Hydrate(N-A-S-H)along the interface which filled the existed pores hence reducing porosity hence high strength of bond.The low transmittance value for the NsO treated samples revealed that there were more cementitious materials existing at the WCFI which led to improvement of bonding strength as compared to the untreated samples.The lower/poor bond strength for the untreated samples is due to existence of untreated,thick water-based filtercake films at WCFI,which prevented the complete hydration process between rock grains and cement slurry components to make chemical binder of cement slurry material and formation.2022 The Authors.Publishing services provided by Elsevier B.V.on b
基金supported by National Natural Science Foundation of China (51704251)National Science and Technology Major Project of the Ministry of Science and Technology of China (2016ZX05006-002)。
文摘Unconventional hydrocarbon reservoirs in layered formations,such as tight sandstones and shales,are continually being developed.Hydraulic fracturing is a critical technology for the high-efficiency development of hydrocarbon reservoirs.Understanding the stress field and stability of the formation interface is vital to understanding stress propagation,preferably before the growing hydraulic fracture contacts the formation interface.In this study,models are developed for computing the stress field of hydraulic fracture propagation near the formation interface,and the stress fields within and at the two sides of the formation interface are analyzed.Four failure modes of the interface under the impact of hydraulic fracture propagation in its vicinity are identified,and the corresponding failure criteria are proposed.By simulating the magnitude and direction of peak stress at different parameters,the failure mode and stability of the formation interface are analyzed.Results reveal that when the interface strength is weak,the formation interface fails before the growing hydraulic fracture contacts it,and its stability is significantly related to a variety of factors,including the type of formation interface,rock mechanical properties,far-field stress,structural parameters,distance between the hydraulic fracture and formation interface,and fracturing execution parameters.
基金supported by the National Natural Science Foundation of China(52006208)the National Innovative Talents Program(GG2090007001)+2 种基金Chinese Academy of Sciences Program(KJ2090130001)USTC Startup Program(KY2090000044)USTC Tang Scholar(KY2090000065)。
