Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings were prepared using cold gas kinetic spray technology.The results show that Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings are achieved with the porosit...Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings were prepared using cold gas kinetic spray technology.The results show that Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings are achieved with the porosity about 3.2%,thickness about 893 μm,the amount of amorphous phase about 82.5%,the hardness about 300 HV0.2.The corrosion potential and anti-corrosion life of 7075 T6 alloy aluminum are about-0.78 V and 72 h,respectively.The electrochemical analysis and neutral salt spray are about-0.69 V corrosion potential and 274 h anti-corrosion life for amorphous Al-based coatings,respectively.Therefore,the life of the Albased amorphous coatings is about 3.8 times that of 7075 T6 aluminum alloy.Besides,the failure mechanism was analyzed using TEM in this investigation.In a word,Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) coatings keep dense structure,high amorphous content,favorable amorphous phase stabilizing ability and longer anticorrosion life.That is,Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) coatings have better comprehensive properties.Therefore,these findings indicate that the present Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings prepared using cold gas kinetic spray technique can protect aluminum alloy very well and they can be considered to be used in aviation field.展开更多
Achieving a delicate synergy between mechanical robustness and antifouling attributes in coatings remains a formidable challenge for marine applications. Inspired by the assembly of nacre, we present a novel approach ...Achieving a delicate synergy between mechanical robustness and antifouling attributes in coatings remains a formidable challenge for marine applications. Inspired by the assembly of nacre, we present a novel approach to fabricate a nacre-like metallic coating. This coating comprises an amorphous matrix with excellent anti-corrosion and anti-wear properties, as well as Cu-rich 3D interconnected channels for antifouling function. The coating is produced by high velocity oxygen fuel (HVOF) thermal spraying of surface-modified Fe-based amorphous powders with a Cu-layer. The resulting coating exhibits exceptional mechanical robustness, including high resistance to erosion, abrasion, and impact, surpassing conventional polymer antifouling coatings. Furthermore, the controlled Cu+ leaching capability of the in-situ constructed 3D interconnected diffusion channels, facilitated by the Cu-rich intersplats, contributes to the remarkable antifouling performance. This includes nearly 100 % resistance to bacterial adhesion after 1 day of immersion and over 98 % resistance to algal attachment after 7 d of immersion, resulting in a prolonged service lifetime. Notably, even after 200 cycles of wear damage, the Cu-modified amorphous coating still maintains its excellent antifouling properties. The Cu-rich intersplats play a critical role in transporting and sustainably leaching Cu ions, thereby accounting for the outstanding antifouling performance. Ultimately, we aim to advance the design of high-performance coatings suited for diverse marine applications, where both the mechanical robustness and antifouling properties are essential.展开更多
A new nanostructured ZrB_(2)-ZrC composite coating with ZrB_(2)-ZrC nanoscale eutectic and ZrB2+Amorphous microstructure was synthesized in situ by plasma spraying Zr-B4 C-Al composite powder.The thermal analysis,quen...A new nanostructured ZrB_(2)-ZrC composite coating with ZrB_(2)-ZrC nanoscale eutectic and ZrB2+Amorphous microstructure was synthesized in situ by plasma spraying Zr-B4 C-Al composite powder.The thermal analysis,quenching experiments and microstructure characterization were investigated and the formation mechanism of the bimodal in-situ microstructure was revealed.Al contributed to the liquid phase separation of molten droplets,which is the key to forming ZrB2+Amorphous microstructure.The formation of coating followed reaction-melting-liquid separation-deposition and solidification mechanism.The nanostructured ZrB_(2)-ZrC composite coating with Al-O intergranular amorphous phase has excellent mechanical properties.The uniform nano-grains improved the hardness and the toughness of the ZrB_(2)-ZrC eutectic.The ZrB_(2)+Al-O amorphous microstructure obtained high toughness and the toughening mechanism was the crack deflection and crack branching caused by intergranular Al-O amorphous phase.展开更多
A FeCrSiBMn amorphous/nanocrystalline coating with 700 μm in thickness and 0.65% in porosity, was prepared by high velocity oxygen fuel(HVOF) spraying process. The long-term corrosion behavior of the FeCrSiBMn coatin...A FeCrSiBMn amorphous/nanocrystalline coating with 700 μm in thickness and 0.65% in porosity, was prepared by high velocity oxygen fuel(HVOF) spraying process. The long-term corrosion behavior of the FeCrSiBMn coating was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) tests in a 3.5% NaCl solution with a hard chromium coating as a reference. The FeCrSiBMn coating exhibited higher corrosion potential and lower corrosion current density than the hard chromium coating. The pore resistance(Rp) and charge transfer resistance(Rct) of FeCrSiBMn coating were higher than those of the hard chromium coating. In addition, after immersion in the Na Cl solution for 28 d, only small pores in the FeCrSiBMn coating were observed. All the results indicated that the FeCrSiBMn coating held superior corrosion resistance to the hard chromium coating. This could be attributed to the dense structure, low porosity and amorphous/nanocrystalline phases of the FeCrSiBMn coating.展开更多
Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecor...Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecorrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosionecorrosion problems. High velocity oxy-fuel(HVOF)spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology(RSM) was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.展开更多
To study the influence of Fe addition on the Al-based amorphous alloys,the structure and properties of Al84Ni10La6 and Al84Ni9Fe1La6 alloys were investigated through various techniques.The results show that 1% Fe（mol...To study the influence of Fe addition on the Al-based amorphous alloys,the structure and properties of Al84Ni10La6 and Al84Ni9Fe1La6 alloys were investigated through various techniques.The results show that 1% Fe（molar fraction） addition increases the area of the pre-peak in the structure factor and decreases the thermal expansion coefficient difference between the crystalline and amorphous states.1% Fe addition also improves the glass forming ability（GFA）,micro-hardness,fracture toughness,electric resistivity,absolute diamagnetism and corrosion resistance of Al-Ni-La alloys,which is related to the changes of medium-range order and quench-in free volume caused by 1% Fe addition.展开更多
Dry sliding wear behavior of amorphous steel coating(ASC) and crystalline stainless steel coating(SSC)manufactured by high-velocity-air-fuel-spraying was investigated. With increasing normal load, coefficient of frict...Dry sliding wear behavior of amorphous steel coating(ASC) and crystalline stainless steel coating(SSC)manufactured by high-velocity-air-fuel-spraying was investigated. With increasing normal load, coefficient of friction(COF) of ASC decreases slightly from 0.78 to 0.69. COF of SSC presents a minor difference under various normal loads but increases with sliding time accompanied by relatively large fluctuation.Such a difference in friction behavior between such two coatings can be understood based upon the roles of shear stress and flash temperature. Wear rate of SSC is much higher than that of ASC, suggesting better wear resistance of ASC. The enhanced wear resistance is correlated with high hardness(H), reduced Young’s modulus(E_r), and ratios of H/Erand H^3/Er^2. Detailed analyses on worn surfaces and sub-surfaces indicate that the wear mechanisms for ASC include delamination, abrasive and oxidation wear, whereas those for SSC are delamination and oxidation.展开更多
Fe/Mo composite coatings were prepared by air plasma spraying （APS） using Fe-based and Mo-based amorphous and nanocrys- talline mixed powders. Microstructural studies show that the composite coatings present a layer...Fe/Mo composite coatings were prepared by air plasma spraying （APS） using Fe-based and Mo-based amorphous and nanocrys- talline mixed powders. Microstructural studies show that the composite coatings present a layered structure with low porosity due to adding the self-bonded Mo-based alloy. Corrosion behaviors of the composite coatings, the Fe-based coatings and the Mo-based coatings were in- vestigated by electrochemical measurements and salt spray tests. Electrochemical results show that the composite coatings exhibit a lower polarization current density and higher corrosion potentials than the Fe-based coating when tested in 3.5wt% NaC1 solutions, indicating supe- rior corrosion resistance compared with the Fe-based coating. Also with the increase in addition of the Mo-based alloy, a raised corrosion re- sistance, inferred by an increase in corrosion potential and a decrease in polarization current density, can be found. The results of salt spray tests again show that the corrosion resistance is enhanced by adding the Mo-based alloy, which helps to reduce the porosity of the composite coatings and enhance the stability of the passive films.展开更多
The Effects of heat treatment temperature on the hardness,wear resistance and structure of the amorphous Ni-W-P-SiC composite coatings have been investigated.The results show that Ni-W-P-SiC composite coatings are amo...The Effects of heat treatment temperature on the hardness,wear resistance and structure of the amorphous Ni-W-P-SiC composite coatings have been investigated.The results show that Ni-W-P-SiC composite coatings are amorphous under 300℃, partially crystalline at 300-400℃,and crystalline when heat treatment temperature reaches 400℃,the crystals being fine Ni3P phase particles.The hardness,wear resistance and the crystallization temperature of the composite coatings increase when an additive is added into the bath.The hardness and wear resistance of the coatings increase with increasing heat treatment temperature,and they will reach their peak values when the heat treatment temperature reaches 400℃.Corrosion experiment indicates that the corrosion resistance of amorphous Ni-W-P-SiC composite coatings in various kinds of corrosive media except nitric acid is better than that of stainless steel 1Cr18Ni9Ti.Scanning electron microscopy observation shows that the additive has no effect on the surface appearance of the coatings,but the current density and the pH value have considerable effects on the surface appearance.展开更多
Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were prepared by detonation gun spraying process. Microstructural studies show that the coatings present a densely layered structure typical of the...Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were prepared by detonation gun spraying process. Microstructural studies show that the coatings present a densely layered structure typical of thermally sprayed deposits with the porosity below 2%. Both crystallization and oxidation occurred obviously during spraying process, so that the amorphous fraction of the coatings decreased to 54% compared with fully amorphous alloy ribbons of the same component. Corrosion behavior of the amorphous coatings was investigated by electrochemical measurement. The results show that the coatings exhibit extremely wide passive region and low passive current density in 3.5% NaCl (mass fraction) and 1 mol/L HCl solutions, which illustrates excellent ability to resist localized corrosion.展开更多
Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were prepared by means of atmospheric plasma spraying (APS) process under different conditions. The microstructure and frictional behavior were cha...Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were prepared by means of atmospheric plasma spraying (APS) process under different conditions. The microstructure and frictional behavior were characterized simultaneously in this article. The results show that the as-deposited coatings consist of amorphous matrix and some precipitated nanocrystals, while the amorphous fraction and particle deformation as well as crystallization mechanism are significantly sensitive to the spraying parameters. The amorphous coatings express high microhardness and excellent wear resistance under dry frictional wear condition, which attributes to the inherent characteristic of amorphous phase and the dispersion strengthening of precipitated nanocrystals. The dominant wear mechanism of the amorphous coatings is fatigue wear accompanying with oxidative wear. In addition, the microhardness and wear resistance of the amorphous coatings were improved by optimizing spraying parameters, owing to the effect of both structural character and proper proportional of amorphous and nanocrystals fraction.展开更多
In this study,a few Fe-based amorphous matrix composite coatings reinforced with various portions(4,8 and16 vol.%) of 31 6L stainless steel powders have been successfully produced through high velocity oxy-fuel(HVOF) ...In this study,a few Fe-based amorphous matrix composite coatings reinforced with various portions(4,8 and16 vol.%) of 31 6L stainless steel powders have been successfully produced through high velocity oxy-fuel(HVOF) spraying.The microstructure of the composite coatings was systematically characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The main structure of composite coatings remained amorphous while 31 6L stainless steel splats were distributed homogeneously in the amorphous matrix and well connected with surrounding amorphous phase.Bonding strength of coatings to the substrate was determined by 'pull-off' tensile tests.The results revealed that the31 6L stainless steel phase effectively improved the bonding strength of amorphous coatings,which is mainly contributed by the strong metallurgical bonding between stainless steel and amorphous splats.The addition of31 6L stainless steel also enhanced the ductility and fracture resistance of the coatings due to the ductile stainless steel phases,which can arrest crack propagation and increase energy dissipation.展开更多
In this work,the electrochemical behaviors of SAM2X5 Fe-based amorphous alloy coating and hard chromium coating were comparatively studied in 3.5 wt% NaCl solution.In comparison with the hard chromium coating,the SAM2...In this work,the electrochemical behaviors of SAM2X5 Fe-based amorphous alloy coating and hard chromium coating were comparatively studied in 3.5 wt% NaCl solution.In comparison with the hard chromium coating,the SAM2X5 coating exhibited a wider and stable passive region with lower passive current density in the potentiodynamic polarization and showed a considerably lower current density at different anodic potentials in the potentiostatic polarization.In order to understand the passivation mechanism of the Fe-based amorphous coating,the components of the passive films formed at various polarization potentials were examined by X-ray photoelectron spectroscopy.The synergistic effect of Mo,W,Mn and Cr in the passive films was systemically analyzed.It has been revealed that Mo and W facilitate the formation of compact and stable Cr2O3 passive film at lower potentials,and the substantial enrichment of Mn in the passive film enhances the passivation ability at relatively higher potentials.The deep understanding of the passivation characteristics in multicomponent alloy systems could provide a guide for the design of corrosion-resistant amorphous alloy coatings for engineering applications.展开更多
To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8＋20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by las...To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8＋20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM （scanning electron microscopy）, EDS （energy dispersive X-ray spectroscopy）, XRD （X-ray diffraction） and TEM （transmission electron microscopy） techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.展开更多
A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatm...A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.展开更多
Transmission electron microscopy （TEM） is usually used to identify the amorphicity. However, some artifacts may be introduced due to improper TEM foil preparation. In this paper, three Al-rich metallic glasses with ...Transmission electron microscopy （TEM） is usually used to identify the amorphicity. However, some artifacts may be introduced due to improper TEM foil preparation. In this paper, three Al-rich metallic glasses with and without a glass transition were selected for characterizing the effect of the electropolishing condition on the as-quenched structure during TEM specimen preparation. It is shown that the occurrence of the modulated bright-dark structure under TEM observation is closely sensitive to the electropolishing condition, which suggests us being careful about the possible artifacts induced by specimen preparation when examining amorphous alloys under TEM.展开更多
Fe-based amorphous composite coatings were fabricated on AISI 1045 steel by laser cladding. The results of the X- ray diffraction and transmission electron microscopy analyses .show the coating is composed of an amorp...Fe-based amorphous composite coatings were fabricated on AISI 1045 steel by laser cladding. The results of the X- ray diffraction and transmission electron microscopy analyses .show the coating is composed of an amorphous phase in majority and a nanocrystaUine phuse in m,inority. Phase composition of the coating changes along the depth of the coating. The reasonable scanning speed for fabricating an amorphous composite coating is 3 500 mm/min when the laser power is 4 800 W and the laser beam diameter is 2 mm. If the scanning speed is lower than 3 500 mm/min, the intensity of the two main diffraction peaks in X-ray diffraction patterns of the coatings decreases with the scanning speeds increasing. At the same time, a broad halo peak emerges and enlarges. High laser power and fast scanning speed are the essential conditions of amorphization. The coating exhibits high microhardness.展开更多
Mechanical alloying method was applied to fabricate coating with amorphous structure on pure Cu substrate.The microstructure,the phase composition and the mechanical properties including microhardness and wear resista...Mechanical alloying method was applied to fabricate coating with amorphous structure on pure Cu substrate.The microstructure,the phase composition and the mechanical properties including microhardness and wear resistance of the coating were,respectively,characterized and analyzed.The results show that the coating is rough but continuous.It has favorable adhesion to the substrate.The coating is made up of an inner composite layer and an outer amorphous layer.The microhardness and the wear resistance of the pure Cu substrate are improved because of the bilayer structure.The formation mechanism of the coating was discussed.The as-synthesized coating is considered to be effective to strengthen the surface of pure Cu substrate.展开更多
This study investigated the effect of annealing below glass transition temperature(T_(g))on the microstructural characteristics,mechanical property,wettability,and electrochemical performance of activated combustion-h...This study investigated the effect of annealing below glass transition temperature(T_(g))on the microstructural characteristics,mechanical property,wettability,and electrochemical performance of activated combustion-high velocity air fuel(AC-HVAF)-sprayed Fe-Cr-Mo-W-C-B-Y amorphous coatings(ACs).Results showed that Fe-based ACs with a thickness of~300μm exhibited a fully amorphous structure with low oxidization.Originating from the reduced free volume,sub-T_(g) annealing increased the thermal stability,hardness,and surface hydrophobicity of Fe-based ACs.The enhanced corrosion resistance of sub-T_(g) annealed ACs in 3.5 wt%NaCl solution was attributed to the increased surface hydrophobicity and passivation capability.This finding elucidates the correlation between sub-T_(g) annealing and the properties of Fe-based ACs,which promotes ameliorating ACs with superior performance.展开更多
基金Project supported by the AVIC Unite Fund(KZ041605114)Civil Aircraft(MJ-2016-F-16)。
文摘Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings were prepared using cold gas kinetic spray technology.The results show that Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings are achieved with the porosity about 3.2%,thickness about 893 μm,the amount of amorphous phase about 82.5%,the hardness about 300 HV0.2.The corrosion potential and anti-corrosion life of 7075 T6 alloy aluminum are about-0.78 V and 72 h,respectively.The electrochemical analysis and neutral salt spray are about-0.69 V corrosion potential and 274 h anti-corrosion life for amorphous Al-based coatings,respectively.Therefore,the life of the Albased amorphous coatings is about 3.8 times that of 7075 T6 aluminum alloy.Besides,the failure mechanism was analyzed using TEM in this investigation.In a word,Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) coatings keep dense structure,high amorphous content,favorable amorphous phase stabilizing ability and longer anticorrosion life.That is,Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) coatings have better comprehensive properties.Therefore,these findings indicate that the present Al_(86)Ni_(8)Co_(1)La_(1)Y_(2)Gd_(2) amorphous coatings prepared using cold gas kinetic spray technique can protect aluminum alloy very well and they can be considered to be used in aviation field.
基金supported by the National Key R&D Program of China(No.2021YFE0100600)the National Natural Science Foundation of China(Nos.92166103,U23A20621,and 92066202)+1 种基金the Top-Notch Young Talents Program of Hubei.Yasir is grateful for financial support from the Pakistan Science Foundation(Project Reference:PSF/CRP-18th Protocol(05))the State Key Laboratory of Materials Processing and Die&Mould Technology(Project Reference:2021-008).
文摘Achieving a delicate synergy between mechanical robustness and antifouling attributes in coatings remains a formidable challenge for marine applications. Inspired by the assembly of nacre, we present a novel approach to fabricate a nacre-like metallic coating. This coating comprises an amorphous matrix with excellent anti-corrosion and anti-wear properties, as well as Cu-rich 3D interconnected channels for antifouling function. The coating is produced by high velocity oxygen fuel (HVOF) thermal spraying of surface-modified Fe-based amorphous powders with a Cu-layer. The resulting coating exhibits exceptional mechanical robustness, including high resistance to erosion, abrasion, and impact, surpassing conventional polymer antifouling coatings. Furthermore, the controlled Cu+ leaching capability of the in-situ constructed 3D interconnected diffusion channels, facilitated by the Cu-rich intersplats, contributes to the remarkable antifouling performance. This includes nearly 100 % resistance to bacterial adhesion after 1 day of immersion and over 98 % resistance to algal attachment after 7 d of immersion, resulting in a prolonged service lifetime. Notably, even after 200 cycles of wear damage, the Cu-modified amorphous coating still maintains its excellent antifouling properties. The Cu-rich intersplats play a critical role in transporting and sustainably leaching Cu ions, thereby accounting for the outstanding antifouling performance. Ultimately, we aim to advance the design of high-performance coatings suited for diverse marine applications, where both the mechanical robustness and antifouling properties are essential.
基金supports of the National Natural Science Foundation of China(Nos.52371063 and 52072110)the Natural Science Foundation of Hebei Province(No.E2018202034)the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.236Z7610G).
文摘A new nanostructured ZrB_(2)-ZrC composite coating with ZrB_(2)-ZrC nanoscale eutectic and ZrB2+Amorphous microstructure was synthesized in situ by plasma spraying Zr-B4 C-Al composite powder.The thermal analysis,quenching experiments and microstructure characterization were investigated and the formation mechanism of the bimodal in-situ microstructure was revealed.Al contributed to the liquid phase separation of molten droplets,which is the key to forming ZrB2+Amorphous microstructure.The formation of coating followed reaction-melting-liquid separation-deposition and solidification mechanism.The nanostructured ZrB_(2)-ZrC composite coating with Al-O intergranular amorphous phase has excellent mechanical properties.The uniform nano-grains improved the hardness and the toughness of the ZrB_(2)-ZrC eutectic.The ZrB_(2)+Al-O amorphous microstructure obtained high toughness and the toughening mechanism was the crack deflection and crack branching caused by intergranular Al-O amorphous phase.
文摘A FeCrSiBMn amorphous/nanocrystalline coating with 700 μm in thickness and 0.65% in porosity, was prepared by high velocity oxygen fuel(HVOF) spraying process. The long-term corrosion behavior of the FeCrSiBMn coating was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS) tests in a 3.5% NaCl solution with a hard chromium coating as a reference. The FeCrSiBMn coating exhibited higher corrosion potential and lower corrosion current density than the hard chromium coating. The pore resistance(Rp) and charge transfer resistance(Rct) of FeCrSiBMn coating were higher than those of the hard chromium coating. In addition, after immersion in the Na Cl solution for 28 d, only small pores in the FeCrSiBMn coating were observed. All the results indicated that the FeCrSiBMn coating held superior corrosion resistance to the hard chromium coating. This could be attributed to the dense structure, low porosity and amorphous/nanocrystalline phases of the FeCrSiBMn coating.
文摘Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecorrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosionecorrosion problems. High velocity oxy-fuel(HVOF)spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology(RSM) was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.
基金Projects(50871061,50871062,50831003 and 50631010)supported by the National Natural Science Foundation of ChinaProject(2008BS04020)supported by the Excellent Youth Science and Technology Award of Shandong Province,China+2 种基金Project(NCET-06-584)supported by the New Century Talents Program of the Ministry of Education,ChinaProject(2007CB613901)supported by the National Basic Research Program of ChinaProject(LZUMMM2010008)supported by Open Project of Key Laboratory for Magnetism Materials of the Ministry of Education,China
文摘To study the influence of Fe addition on the Al-based amorphous alloys,the structure and properties of Al84Ni10La6 and Al84Ni9Fe1La6 alloys were investigated through various techniques.The results show that 1% Fe（molar fraction） addition increases the area of the pre-peak in the structure factor and decreases the thermal expansion coefficient difference between the crystalline and amorphous states.1% Fe addition also improves the glass forming ability（GFA）,micro-hardness,fracture toughness,electric resistivity,absolute diamagnetism and corrosion resistance of Al-Ni-La alloys,which is related to the changes of medium-range order and quench-in free volume caused by 1% Fe addition.
基金supported by the National Key Research and Development Program of China (No. 2016YFB1100204)National Natural Science Foundation of China (Nos. 51701214 and 51471166)
文摘Dry sliding wear behavior of amorphous steel coating(ASC) and crystalline stainless steel coating(SSC)manufactured by high-velocity-air-fuel-spraying was investigated. With increasing normal load, coefficient of friction(COF) of ASC decreases slightly from 0.78 to 0.69. COF of SSC presents a minor difference under various normal loads but increases with sliding time accompanied by relatively large fluctuation.Such a difference in friction behavior between such two coatings can be understood based upon the roles of shear stress and flash temperature. Wear rate of SSC is much higher than that of ASC, suggesting better wear resistance of ASC. The enhanced wear resistance is correlated with high hardness(H), reduced Young’s modulus(E_r), and ratios of H/Erand H^3/Er^2. Detailed analyses on worn surfaces and sub-surfaces indicate that the wear mechanisms for ASC include delamination, abrasive and oxidation wear, whereas those for SSC are delamination and oxidation.
基金financially supported by the Special Fund for Basic Scientific Research of Central Colleges, Chang’an University (No.CHD2011JC126)the Special Fund for Basic Research Support Plan of Chang’an Universitythe Open Fund of the Engineering Research Center of Transportation Materials, Ministry of Education of China
文摘Fe/Mo composite coatings were prepared by air plasma spraying （APS） using Fe-based and Mo-based amorphous and nanocrys- talline mixed powders. Microstructural studies show that the composite coatings present a layered structure with low porosity due to adding the self-bonded Mo-based alloy. Corrosion behaviors of the composite coatings, the Fe-based coatings and the Mo-based coatings were in- vestigated by electrochemical measurements and salt spray tests. Electrochemical results show that the composite coatings exhibit a lower polarization current density and higher corrosion potentials than the Fe-based coating when tested in 3.5wt% NaC1 solutions, indicating supe- rior corrosion resistance compared with the Fe-based coating. Also with the increase in addition of the Mo-based alloy, a raised corrosion re- sistance, inferred by an increase in corrosion potential and a decrease in polarization current density, can be found. The results of salt spray tests again show that the corrosion resistance is enhanced by adding the Mo-based alloy, which helps to reduce the porosity of the composite coatings and enhance the stability of the passive films.
文摘The Effects of heat treatment temperature on the hardness,wear resistance and structure of the amorphous Ni-W-P-SiC composite coatings have been investigated.The results show that Ni-W-P-SiC composite coatings are amorphous under 300℃, partially crystalline at 300-400℃,and crystalline when heat treatment temperature reaches 400℃,the crystals being fine Ni3P phase particles.The hardness,wear resistance and the crystallization temperature of the composite coatings increase when an additive is added into the bath.The hardness and wear resistance of the coatings increase with increasing heat treatment temperature,and they will reach their peak values when the heat treatment temperature reaches 400℃.Corrosion experiment indicates that the corrosion resistance of amorphous Ni-W-P-SiC composite coatings in various kinds of corrosive media except nitric acid is better than that of stainless steel 1Cr18Ni9Ti.Scanning electron microscopy observation shows that the additive has no effect on the surface appearance of the coatings,but the current density and the pH value have considerable effects on the surface appearance.
文摘Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were prepared by detonation gun spraying process. Microstructural studies show that the coatings present a densely layered structure typical of thermally sprayed deposits with the porosity below 2%. Both crystallization and oxidation occurred obviously during spraying process, so that the amorphous fraction of the coatings decreased to 54% compared with fully amorphous alloy ribbons of the same component. Corrosion behavior of the amorphous coatings was investigated by electrochemical measurement. The results show that the coatings exhibit extremely wide passive region and low passive current density in 3.5% NaCl (mass fraction) and 1 mol/L HCl solutions, which illustrates excellent ability to resist localized corrosion.
基金Beijing Municipal Education Commission (00900054R5004)
文摘Amorphous metallic coatings with a composition of Fe48Cr15Mo14C15B6Y2 were prepared by means of atmospheric plasma spraying (APS) process under different conditions. The microstructure and frictional behavior were characterized simultaneously in this article. The results show that the as-deposited coatings consist of amorphous matrix and some precipitated nanocrystals, while the amorphous fraction and particle deformation as well as crystallization mechanism are significantly sensitive to the spraying parameters. The amorphous coatings express high microhardness and excellent wear resistance under dry frictional wear condition, which attributes to the inherent characteristic of amorphous phase and the dispersion strengthening of precipitated nanocrystals. The dominant wear mechanism of the amorphous coatings is fatigue wear accompanying with oxidative wear. In addition, the microhardness and wear resistance of the amorphous coatings were improved by optimizing spraying parameters, owing to the effect of both structural character and proper proportional of amorphous and nanocrystals fraction.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 51271081 and 51301072)partially supported by the Key Fundamental Research Project from Shenzhen Research Council (No. JC201105170745A)
文摘In this study,a few Fe-based amorphous matrix composite coatings reinforced with various portions(4,8 and16 vol.%) of 31 6L stainless steel powders have been successfully produced through high velocity oxy-fuel(HVOF) spraying.The microstructure of the composite coatings was systematically characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The main structure of composite coatings remained amorphous while 31 6L stainless steel splats were distributed homogeneously in the amorphous matrix and well connected with surrounding amorphous phase.Bonding strength of coatings to the substrate was determined by 'pull-off' tensile tests.The results revealed that the31 6L stainless steel phase effectively improved the bonding strength of amorphous coatings,which is mainly contributed by the strong metallurgical bonding between stainless steel and amorphous splats.The addition of31 6L stainless steel also enhanced the ductility and fracture resistance of the coatings due to the ductile stainless steel phases,which can arrest crack propagation and increase energy dissipation.
基金supported by the National Natural Science Foundation of China (Nos. 51471166, 51131006 and 51171119)the College Youth Scholar Fostering Program of Liaoning Province (No. LJQ2014015)
文摘In this work,the electrochemical behaviors of SAM2X5 Fe-based amorphous alloy coating and hard chromium coating were comparatively studied in 3.5 wt% NaCl solution.In comparison with the hard chromium coating,the SAM2X5 coating exhibited a wider and stable passive region with lower passive current density in the potentiodynamic polarization and showed a considerably lower current density at different anodic potentials in the potentiostatic polarization.In order to understand the passivation mechanism of the Fe-based amorphous coating,the components of the passive films formed at various polarization potentials were examined by X-ray photoelectron spectroscopy.The synergistic effect of Mo,W,Mn and Cr in the passive films was systemically analyzed.It has been revealed that Mo and W facilitate the formation of compact and stable Cr2O3 passive film at lower potentials,and the substantial enrichment of Mn in the passive film enhances the passivation ability at relatively higher potentials.The deep understanding of the passivation characteristics in multicomponent alloy systems could provide a guide for the design of corrosion-resistant amorphous alloy coatings for engineering applications.
基金supported by the Open Fund of the State Key Laboratory of Advanced Welding Production Technology in Harbin Institute of Technology,Chinathe Open Fund of the State Key Laboratory of Materials Processing and Die&Mould Technology in Huazhong University of Science and Technology,China
文摘To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8＋20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM （scanning electron microscopy）, EDS （energy dispersive X-ray spectroscopy）, XRD （X-ray diffraction） and TEM （transmission electron microscopy） techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.
基金the Key-Area Research and Development Program of Guangdong Province(2019B010936001)financially supported by the National Natural Science Foundation of China(Grant Nos.51671202 and 51301184)。
文摘A low-diffusion Ni Re Pt Al coating((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer)was prepared on a Ni_(3)Al-base single crystal(SC)superalloy via electroplating and gaseous aluminizing treatments,wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt.In order to perform a comparison with conventional Ni Al and(Ni,Pt)Al coatings,the cyclic oxidation performance of the Ni Re Pt Al coating was evaluated at 1100 and 1150℃.We observed that the oxidation resistance of the Ni Re Pt Al coating was significantly improved by the greater presence of the residualβ-Ni Al phase in the outer layer and the lesser outward-diffusion of Mo from the substrate.In addition,the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate,where the thickness of the second reaction zone(SRZ)in the substrate alloy decreased by 25%.The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed,in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.
基金This work was financially supported by the National Natural Science Foundation of China （Nos. 50271070, 50323009, 50471076）.
文摘Transmission electron microscopy （TEM） is usually used to identify the amorphicity. However, some artifacts may be introduced due to improper TEM foil preparation. In this paper, three Al-rich metallic glasses with and without a glass transition were selected for characterizing the effect of the electropolishing condition on the as-quenched structure during TEM specimen preparation. It is shown that the occurrence of the modulated bright-dark structure under TEM observation is closely sensitive to the electropolishing condition, which suggests us being careful about the possible artifacts induced by specimen preparation when examining amorphous alloys under TEM.
文摘Fe-based amorphous composite coatings were fabricated on AISI 1045 steel by laser cladding. The results of the X- ray diffraction and transmission electron microscopy analyses .show the coating is composed of an amorphous phase in majority and a nanocrystaUine phuse in m,inority. Phase composition of the coating changes along the depth of the coating. The reasonable scanning speed for fabricating an amorphous composite coating is 3 500 mm/min when the laser power is 4 800 W and the laser beam diameter is 2 mm. If the scanning speed is lower than 3 500 mm/min, the intensity of the two main diffraction peaks in X-ray diffraction patterns of the coatings decreases with the scanning speeds increasing. At the same time, a broad halo peak emerges and enlarges. High laser power and fast scanning speed are the essential conditions of amorphization. The coating exhibits high microhardness.
基金financially supported by the Introduce Talent Special Funding for Scientific Research at Nanjing Tech University(No.39802125)the National Natural Science Foundation of China(No.51475232)。
文摘Mechanical alloying method was applied to fabricate coating with amorphous structure on pure Cu substrate.The microstructure,the phase composition and the mechanical properties including microhardness and wear resistance of the coating were,respectively,characterized and analyzed.The results show that the coating is rough but continuous.It has favorable adhesion to the substrate.The coating is made up of an inner composite layer and an outer amorphous layer.The microhardness and the wear resistance of the pure Cu substrate are improved because of the bilayer structure.The formation mechanism of the coating was discussed.The as-synthesized coating is considered to be effective to strengthen the surface of pure Cu substrate.
基金supported by the National Natural Science Foundation of China(No.51901138)the Postdoctoral Science Foundation of China(No.2020M672788)the National Key Research and Development Program of China(No.2018YFA0703605)。
文摘This study investigated the effect of annealing below glass transition temperature(T_(g))on the microstructural characteristics,mechanical property,wettability,and electrochemical performance of activated combustion-high velocity air fuel(AC-HVAF)-sprayed Fe-Cr-Mo-W-C-B-Y amorphous coatings(ACs).Results showed that Fe-based ACs with a thickness of~300μm exhibited a fully amorphous structure with low oxidization.Originating from the reduced free volume,sub-T_(g) annealing increased the thermal stability,hardness,and surface hydrophobicity of Fe-based ACs.The enhanced corrosion resistance of sub-T_(g) annealed ACs in 3.5 wt%NaCl solution was attributed to the increased surface hydrophobicity and passivation capability.This finding elucidates the correlation between sub-T_(g) annealing and the properties of Fe-based ACs,which promotes ameliorating ACs with superior performance.
