Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector...Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were investigated.The results show that lath martensite can be obtained after austenitizing in the range of 860-980℃and then water cooling.With an increase in austenitizing temperature,the precipitate content gradually decreases.The precipitates are mainly composed of TiC and Ti4C2S2,and their total content is between 1.15wt.%and 1.64wt.%.The precipitate phase concentration by water-cooling is higher than that by10%NaCl cooling due to the lower cooling rate of water cooling.As the austeniting temperature increases,the hardness and tensile strength of both water cooled and 10%NaCl cooled steels firstly increase and then decrease.The experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900℃,cooled by 10%NaCl,and then tempered at 200℃.Its hardness,ultimate tensile strength,and wear rate reach551.4 HBW,1,438.2 MPa,and 0.48×10^(-2)mg·m^(-1),respectively.展开更多
To improve the wear resistance of the FeCoCrNiB_(0.2)high entropy alloy(HEA),the FeCoCrNiB_(0.2)(WC_(0))and FeCoCrNiB_(0.2)+20wt%WC(WC_(20))HEA coatings were prepared on Q235 steel by laser cladding(LC).The microstruc...To improve the wear resistance of the FeCoCrNiB_(0.2)high entropy alloy(HEA),the FeCoCrNiB_(0.2)(WC_(0))and FeCoCrNiB_(0.2)+20wt%WC(WC_(20))HEA coatings were prepared on Q235 steel by laser cladding(LC).The microstructure,hardness,and tribometer of the HEA coatings were investigated using scanning electron microscopy with spectroscopy(SEM/EDS),X-ray diffraction(XRD),vickers microhardness tester,and pin-on-disc tribometer,respectively.The experimental results show that the WC0HEA coating comprises a simple BCC phase mixed with an M_(2)B phase.Adding 20wt%WC,the WC_(20)HEA coating is composed of a simple BCC phase mixed with the Cr_(23)C_(6)carbide phase.The microstructure of the WC_(20)HEA coating is simple,which consists of equiaxed grain and dendritic.The microhardness also increases from 625.5HV to 806.0HV,and the wear mass loss correspondingly decreases from 30.9 to 14.9 mg.W and C atoms formed by WC dissolution are mainly dissolved in the BCC phase,which leads to the solution strengthening effect.Besides,Cr_(23)C_(6)carbides inhibit the growth of the grains,play the role of fine-grain strengthening,and further improve the hardness and wear resistance of the HEA coating.展开更多
A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed. The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occl...A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed. The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occluding the micro holes of the cast magnesium alloy and interdicting the bubble formation in the Ni-P coating during plating process. And pickling pretreatment can provide a better adhesion between the Ni-P deposition and AZ91D substrate. The deposition speed of the Ni-P coating is 29 μm/h. The technology is employed to AZ91D magnesium alloy automobile parts and can provide high hardness and high wear-resistant. The weight losses of Ni-P plated and heat-treated Ni-P plated magnesium alloy specimen are only about 1/6 and 1/10 that of bare magnesium alloy specimen after 10 min abrasion wear, respectively. The hardness of the electroless Ni-P plated brake pedal support brackets is 674.1 VHN and 935.7 VHN after 2 hours heat treatments at 180 C. The adhesion of Ni-P coatings on magnesium alloy substrates meets the demands of ISO Standards 2819. The technology is environment friendly and cannot cause hazard to environment because of absence of chromate in the whole process.展开更多
Alloy powders including Ni60, WC, CrC, and TiC with different mass ratios were deposited on medium carbon low alloy steel by plasma welding. Through the experiments, the optimal alloy powder reinforcing cutter tool su...Alloy powders including Ni60, WC, CrC, and TiC with different mass ratios were deposited on medium carbon low alloy steel by plasma welding. Through the experiments, the optimal alloy powder reinforcing cutter tool surface properties were discovered. The wear resistance properties were investigated on the impact abrasive wear tester. The experimental results show that in terms of microstructure, there exists the shape of herringbone, spider mesh, broken flower structures in coatings. In addition, fusion area of four specimens surfacing welding layer displays a large number of acicular martensite with a small amount of austenite. The coating mainly consists of Ni-Cr-Fe austenitic phase and the other precipitates. TiC density is smaller, its content is less in alloy powder, in the process of surfacing welding, TiC is melted fully, which is mainly distributed in surface layer and middle layer of hard facing layer. The content of TiC gradually reduces from surface layer of hard facing layer to the fusion area. Compared to TiC, the density of tungsten carbide and chromium carbide is larger, there exist tungsten carbide and chromium carbide particles, which are not completely melted near the fusion area. The micro-hardness presents gradient change from the fusion area to the surface layer of hard facing layer, and the hardness of the middle layer is slightly lower than that of the fusion area, and the hardness increases near the surface layer.展开更多
The influence of RE and Tion ZA-27 casting alloy was studied. The results show that RE and Ti refine microstructure of the alloy and improve its mechanical properties and wear-resistance, which make it possible to use...The influence of RE and Tion ZA-27 casting alloy was studied. The results show that RE and Ti refine microstructure of the alloy and improve its mechanical properties and wear-resistance, which make it possible to use ZA-27TiRE casting alloy in the field of artificial limb industry.展开更多
New Mg2Si based alloy were prepared by mechanical alloying. Sintering temperature was from 825 to 865K, which indicated that few Mg2Si were produced at lower temperature while MgO were produced at higher temperature. ...New Mg2Si based alloy were prepared by mechanical alloying. Sintering temperature was from 825 to 865K, which indicated that few Mg2Si were produced at lower temperature while MgO were produced at higher temperature. Microstructure image showed that at sintering temperature of 855K, Mg2Si were mostly synthesized with the reaction of purity magnesia powder and silicon powder. Hardness and wear tests proved that the new synthetic silicon magnesium alloy had higher hardness and good wear resistance. Under the same testing conditions, it is found that the hardness of the new material is 420.50, and pure magnesium is only 41.65.In the same experiments it is also found that under the same pressure, pure magnesium alloys than silicon wearing capacity of pure magnesium is 2 times as high that of Mg2Si based alloy. It shows that Mg2Si based alloy is the ideal material for the wear parts of car engine cylinder liner because of its small density, stable dimension, high hardness and wear-resisting.展开更多
The high-temperature oxidation behavior of novel Co-Cr-Nb-W carbide-strengthened wear-resistance alloys with different Al contents(1wt%,2wt%and 3wt%)at 950,1000 and 1050℃was thoroughly investigated by scanning electr...The high-temperature oxidation behavior of novel Co-Cr-Nb-W carbide-strengthened wear-resistance alloys with different Al contents(1wt%,2wt%and 3wt%)at 950,1000 and 1050℃was thoroughly investigated by scanning electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy and field emission electron probe analyzer.The porous property of NbC in-situ oxidation products(Nb_(2)O_(5),Co Nb_(2)O_(6)and Co_(4)Nb_(2)O_(9))induces a multi-layered oxide scale with micropores and cracks.Co-Cr-Nb-W alloy with 1 wt%Al undergoes catastrophic oxidation and spalling above 1000℃.The outward transportation of Cr and Co is effectively restrained by a continuous Al_(2)O_(3)scale formed around NbC in-situ oxidation region when Al content reaches 3 wt%.The β-Co Al in Co-Cr-Nb-W alloy with 3 wt%Al has an oxidation priority over eutectic carbides and the alloy matrix which are both enriched with Cr,thereby preventing the formation of Cr-depletion area and improving the self-healing ability of the oxide film.A slight change in Al content has a remarkable influence on the cooperative effect of Al and Cr and multiplies the antioxidant capacity of Co-Cr-Nb-W alloy above 1000℃.展开更多
The excellent properties of the multi-principal element alloys(e.g.,the CoCrNi medium-entropy alloy)make them a perfect candidate for structure materials.Their low strength and poor wear-resistance,however,limit consi...The excellent properties of the multi-principal element alloys(e.g.,the CoCrNi medium-entropy alloy)make them a perfect candidate for structure materials.Their low strength and poor wear-resistance,however,limit considerably their applications.In this study,a lamellar eutectic microstructure was introduced by addition of Hf into CoCrNi alloy to produce a series of CoCrNiHf_(x)(x=0.1,0.2,0.3 and 0.4)eutectic medium-entropy alloys.A homogeneous eutectic microstructure with an alternate array of the soft FCC solid-solution phase and the hard Laves phase was identified for the as-cast CoCrNiHf_(0.3)alloy.After an investigation of the microstructure,mechanical and tribological properties,it was found that the hardness(plasticity)increases(decreases)with the increasing volume fraction of the Laves phase and the CoCrNiHf_(0.3)eutectic alloy exhibits both good plasticity and high strength.The wear behavior is strongly dependent on the applied normal load.For a low normal load,its tribological behavior follows the Archard's equation and a higher hardness due to Hf addition can resist plastic deformation and abrasive wear.When the normal load is high enough,the hypoeutectic or hypereutectic alloy,which possessing either high strength or good ductility but not at the same time,exhibit a poor wear resistance.In comparison,the full eutectic CoCrNiHf_(0.3)alloy with a superior combination of strength and toughness shows the best wear performance,as it can significantly reduce fracture during wear.展开更多
In this study,single-phase NbTiZr and NbTiZr(MoTa)_(0.1) medium-entropy alloys(MEAs)were investigated for their use in biomedical implants.The alloys were prepared by arc melting,and were then cold-rolled,annealed,and...In this study,single-phase NbTiZr and NbTiZr(MoTa)_(0.1) medium-entropy alloys(MEAs)were investigated for their use in biomedical implants.The alloys were prepared by arc melting,and were then cold-rolled,annealed,and characterized in terms of phase analysis,mechanical properties,fractography,and wear resistance.Both alloys showed a single body-centered cubic phase with superior mechanical,and tribological properties compared to commercially available biomedical alloys.Mo and Ta-containing MEAs showed higher tensile yield strength(1060±18 MPa)and higher tensile ductility(~20%),thus overcoming the strength-ductility trade-off with no signs of transformation-induced plasticity,twinning,or precipitation.The generalized stacking fault energy(GSFE)calculations on the{112}<111>slip system by the first-principles calculations based on density functional theory showed that the addition of less than0.2 molar fraction of Mo and Ta lowers the GSFE curves.This behavior posits the increase in ductility of the alloy by facilitating slips although strength is also increased by solid solution strengthening.The wear resistance of both alloys against hardened steel surfaces was superior to that of commercial biomedical alloys.Thus,we concluded that NbTiZr(MoTa)_(0.1)MEA with good tensile ductility is a potential candidate for biomedical implants.展开更多
文摘Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were investigated.The results show that lath martensite can be obtained after austenitizing in the range of 860-980℃and then water cooling.With an increase in austenitizing temperature,the precipitate content gradually decreases.The precipitates are mainly composed of TiC and Ti4C2S2,and their total content is between 1.15wt.%and 1.64wt.%.The precipitate phase concentration by water-cooling is higher than that by10%NaCl cooling due to the lower cooling rate of water cooling.As the austeniting temperature increases,the hardness and tensile strength of both water cooled and 10%NaCl cooled steels firstly increase and then decrease.The experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900℃,cooled by 10%NaCl,and then tempered at 200℃.Its hardness,ultimate tensile strength,and wear rate reach551.4 HBW,1,438.2 MPa,and 0.48×10^(-2)mg·m^(-1),respectively.
基金Funded by the National Natural Science Foundation of China (No.51879089)。
文摘To improve the wear resistance of the FeCoCrNiB_(0.2)high entropy alloy(HEA),the FeCoCrNiB_(0.2)(WC_(0))and FeCoCrNiB_(0.2)+20wt%WC(WC_(20))HEA coatings were prepared on Q235 steel by laser cladding(LC).The microstructure,hardness,and tribometer of the HEA coatings were investigated using scanning electron microscopy with spectroscopy(SEM/EDS),X-ray diffraction(XRD),vickers microhardness tester,and pin-on-disc tribometer,respectively.The experimental results show that the WC0HEA coating comprises a simple BCC phase mixed with an M_(2)B phase.Adding 20wt%WC,the WC_(20)HEA coating is composed of a simple BCC phase mixed with the Cr_(23)C_(6)carbide phase.The microstructure of the WC_(20)HEA coating is simple,which consists of equiaxed grain and dendritic.The microhardness also increases from 625.5HV to 806.0HV,and the wear mass loss correspondingly decreases from 30.9 to 14.9 mg.W and C atoms formed by WC dissolution are mainly dissolved in the BCC phase,which leads to the solution strengthening effect.Besides,Cr_(23)C_(6)carbides inhibit the growth of the grains,play the role of fine-grain strengthening,and further improve the hardness and wear resistance of the HEA coating.
基金Foundation of National Key Basic Research and Development Program(No.2004CB619301)Project 985-Automotive Engineering of Jilin University
文摘A technology for electroless Ni-P deposition on AZ91D from a low cost plating bath containing sulfate nickel was proposed. The seal pretreatment was employed before the electroless Ni-P deposition for the sake of occluding the micro holes of the cast magnesium alloy and interdicting the bubble formation in the Ni-P coating during plating process. And pickling pretreatment can provide a better adhesion between the Ni-P deposition and AZ91D substrate. The deposition speed of the Ni-P coating is 29 μm/h. The technology is employed to AZ91D magnesium alloy automobile parts and can provide high hardness and high wear-resistant. The weight losses of Ni-P plated and heat-treated Ni-P plated magnesium alloy specimen are only about 1/6 and 1/10 that of bare magnesium alloy specimen after 10 min abrasion wear, respectively. The hardness of the electroless Ni-P plated brake pedal support brackets is 674.1 VHN and 935.7 VHN after 2 hours heat treatments at 180 C. The adhesion of Ni-P coatings on magnesium alloy substrates meets the demands of ISO Standards 2819. The technology is environment friendly and cannot cause hazard to environment because of absence of chromate in the whole process.
基金Funded by the National Science and Technology Support Project(2006BAK02B01-02)
文摘Alloy powders including Ni60, WC, CrC, and TiC with different mass ratios were deposited on medium carbon low alloy steel by plasma welding. Through the experiments, the optimal alloy powder reinforcing cutter tool surface properties were discovered. The wear resistance properties were investigated on the impact abrasive wear tester. The experimental results show that in terms of microstructure, there exists the shape of herringbone, spider mesh, broken flower structures in coatings. In addition, fusion area of four specimens surfacing welding layer displays a large number of acicular martensite with a small amount of austenite. The coating mainly consists of Ni-Cr-Fe austenitic phase and the other precipitates. TiC density is smaller, its content is less in alloy powder, in the process of surfacing welding, TiC is melted fully, which is mainly distributed in surface layer and middle layer of hard facing layer. The content of TiC gradually reduces from surface layer of hard facing layer to the fusion area. Compared to TiC, the density of tungsten carbide and chromium carbide is larger, there exist tungsten carbide and chromium carbide particles, which are not completely melted near the fusion area. The micro-hardness presents gradient change from the fusion area to the surface layer of hard facing layer, and the hardness of the middle layer is slightly lower than that of the fusion area, and the hardness increases near the surface layer.
文摘The influence of RE and Tion ZA-27 casting alloy was studied. The results show that RE and Ti refine microstructure of the alloy and improve its mechanical properties and wear-resistance, which make it possible to use ZA-27TiRE casting alloy in the field of artificial limb industry.
基金Funded by the " 973 " Program of China (No. 2007CB613502)
文摘New Mg2Si based alloy were prepared by mechanical alloying. Sintering temperature was from 825 to 865K, which indicated that few Mg2Si were produced at lower temperature while MgO were produced at higher temperature. Microstructure image showed that at sintering temperature of 855K, Mg2Si were mostly synthesized with the reaction of purity magnesia powder and silicon powder. Hardness and wear tests proved that the new synthetic silicon magnesium alloy had higher hardness and good wear resistance. Under the same testing conditions, it is found that the hardness of the new material is 420.50, and pure magnesium is only 41.65.In the same experiments it is also found that under the same pressure, pure magnesium alloys than silicon wearing capacity of pure magnesium is 2 times as high that of Mg2Si based alloy. It shows that Mg2Si based alloy is the ideal material for the wear parts of car engine cylinder liner because of its small density, stable dimension, high hardness and wear-resisting.
基金supported by the National Key R&D Program of China(No.2022YFC3902002)。
文摘The high-temperature oxidation behavior of novel Co-Cr-Nb-W carbide-strengthened wear-resistance alloys with different Al contents(1wt%,2wt%and 3wt%)at 950,1000 and 1050℃was thoroughly investigated by scanning electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy and field emission electron probe analyzer.The porous property of NbC in-situ oxidation products(Nb_(2)O_(5),Co Nb_(2)O_(6)and Co_(4)Nb_(2)O_(9))induces a multi-layered oxide scale with micropores and cracks.Co-Cr-Nb-W alloy with 1 wt%Al undergoes catastrophic oxidation and spalling above 1000℃.The outward transportation of Cr and Co is effectively restrained by a continuous Al_(2)O_(3)scale formed around NbC in-situ oxidation region when Al content reaches 3 wt%.The β-Co Al in Co-Cr-Nb-W alloy with 3 wt%Al has an oxidation priority over eutectic carbides and the alloy matrix which are both enriched with Cr,thereby preventing the formation of Cr-depletion area and improving the self-healing ability of the oxide film.A slight change in Al content has a remarkable influence on the cooperative effect of Al and Cr and multiplies the antioxidant capacity of Co-Cr-Nb-W alloy above 1000℃.
基金financially supported by the National Natural Science Foundation of China(No.51975474)the Science Fund for Distinguished Young Scholars from Shaanxi Province(No.2018JC007)+1 种基金the Natural Science Basic Research Program from Shaanxi Province(No.2019JQ-020)the Fundamental Research Funds for the Central Universities(No.3102019JC001)。
文摘The excellent properties of the multi-principal element alloys(e.g.,the CoCrNi medium-entropy alloy)make them a perfect candidate for structure materials.Their low strength and poor wear-resistance,however,limit considerably their applications.In this study,a lamellar eutectic microstructure was introduced by addition of Hf into CoCrNi alloy to produce a series of CoCrNiHf_(x)(x=0.1,0.2,0.3 and 0.4)eutectic medium-entropy alloys.A homogeneous eutectic microstructure with an alternate array of the soft FCC solid-solution phase and the hard Laves phase was identified for the as-cast CoCrNiHf_(0.3)alloy.After an investigation of the microstructure,mechanical and tribological properties,it was found that the hardness(plasticity)increases(decreases)with the increasing volume fraction of the Laves phase and the CoCrNiHf_(0.3)eutectic alloy exhibits both good plasticity and high strength.The wear behavior is strongly dependent on the applied normal load.For a low normal load,its tribological behavior follows the Archard's equation and a higher hardness due to Hf addition can resist plastic deformation and abrasive wear.When the normal load is high enough,the hypoeutectic or hypereutectic alloy,which possessing either high strength or good ductility but not at the same time,exhibit a poor wear resistance.In comparison,the full eutectic CoCrNiHf_(0.3)alloy with a superior combination of strength and toughness shows the best wear performance,as it can significantly reduce fracture during wear.
基金supported by the National Research Foundation of Korea(NRF-2020R1A5A6017701,NRF-2121R1A2C2014025)。
文摘In this study,single-phase NbTiZr and NbTiZr(MoTa)_(0.1) medium-entropy alloys(MEAs)were investigated for their use in biomedical implants.The alloys were prepared by arc melting,and were then cold-rolled,annealed,and characterized in terms of phase analysis,mechanical properties,fractography,and wear resistance.Both alloys showed a single body-centered cubic phase with superior mechanical,and tribological properties compared to commercially available biomedical alloys.Mo and Ta-containing MEAs showed higher tensile yield strength(1060±18 MPa)and higher tensile ductility(~20%),thus overcoming the strength-ductility trade-off with no signs of transformation-induced plasticity,twinning,or precipitation.The generalized stacking fault energy(GSFE)calculations on the{112}<111>slip system by the first-principles calculations based on density functional theory showed that the addition of less than0.2 molar fraction of Mo and Ta lowers the GSFE curves.This behavior posits the increase in ductility of the alloy by facilitating slips although strength is also increased by solid solution strengthening.The wear resistance of both alloys against hardened steel surfaces was superior to that of commercial biomedical alloys.Thus,we concluded that NbTiZr(MoTa)_(0.1)MEA with good tensile ductility is a potential candidate for biomedical implants.
