By mixing preheated high-aluminum bronze powders with different amounts of Al_2O_3 powder, a low-pressure cold-sprayed coating was prepared and sprayed onto a Cr12MoV steel substrate. The hardness of the coating and t...By mixing preheated high-aluminum bronze powders with different amounts of Al_2O_3 powder, a low-pressure cold-sprayed coating was prepared and sprayed onto a Cr12MoV steel substrate. The hardness of the coating and the bonding strength between the coating and the substrate were tested with a HV-1000 microhardness tester and a mechanical universal testing machine. The surface microstructure, cross-section and tensile fracture surface of the coating were observed with a scanning electron microscope(SEM). Correspondingly, the influences of the preheat treatment temperature of the bronze powder and the Al_2O_3 content on the coating performance were investigated. The results indicate that the hardness of bronze powders decreased and the coating deposition rate increased after the preheating treatment of the bronze powder. The Al_2O_3 content in the mixed powders contributed to the deformation of bronze powders during the spraying process. This trend resulted in varied performance of the coating.展开更多
The high-temperature oxidation behavior of arc-sprayed aluminum bronze coatings on steel substrate was studied during isothermal exposures in air at 900 ℃. The surface morphologies and interface of the coatings after...The high-temperature oxidation behavior of arc-sprayed aluminum bronze coatings on steel substrate was studied during isothermal exposures in air at 900 ℃. The surface morphologies and interface of the coatings after isothermal oxidation at 900 ℃ for different times were observed. The experiments showed that the coatings on steel substrate were not deteriorated and the substrate was protected well, being exposed to high temperatures up to 900 ℃ . The coatings withstood more than ten times thermal shock tests without any coating separation. The thermal expansion coefficient of the coatings was measured, revealing not much difference between it and that of steel substrate. After exposure at high temperature, the coatings were still adhered to steel substrate well. Isothermal mass gain of the coatings at elevated temperature in dry air was measured by means of a thermal balance and the oxidation behavior was evaluated by oxidation kinetic curves, exhibiting the oxidation kinetics curve accorded with a parabolic law. The parabolic rate constant of the oxidation kinetic curve is 1.02×10?9 g2·cm?4·s?1 for the first 60 min and from 150 min to 2 880 min the constant is 5.1×10?12 g2·cm?4·s?1.展开更多
The cylinder block/valve plate interface is one of the most critical frictional interfaces of the swashplate-type axial piston pump.However,the poor lubrication interface caused rapid wear and high friction loss in an...The cylinder block/valve plate interface is one of the most critical frictional interfaces of the swashplate-type axial piston pump.However,the poor lubrication interface caused rapid wear and high friction loss in an elastohydrodynamic lubrication system,decreasing the pump lifetime.Wear resistant bronze coatings were fabricated on 38CrMoAl substrate by Physical Vapor Deposition(PVD)and Chemical Vapor Deposition(CVD),respectively.Ball-on-disc wear tests were performed to comparatively investigate the wear behaviors of the coatings and bulk ductile iron samples.It can be found that the PVD-bronze coating exhibited better wear resistance than the other two samples.This enhanced wear resistance was attributed to the unique composite microstructure and desired mechanical strength,which could resist to mechanical shear and spallation,decreasing friction loss.The appropriate hardness of(1.33±0.07)GPa could be beneficial for enhancing its wear resistance.The PVD-bronze coating possessed a much lower and stable coefficient of friction(about 0.1)and wear rate(about 6000μm3.N-1.m-1)under the loading forces of about 100 N after 20 min.The wear mechanism was the abrasive wear.展开更多
The directional structure of Ni60/high-aluminum bronze composite coating was formed using induction remelting and forced cooling.The microstructural evolution and the characteristics of interface growth were studied.T...The directional structure of Ni60/high-aluminum bronze composite coating was formed using induction remelting and forced cooling.The microstructural evolution and the characteristics of interface growth were studied.The results showed that the remelted coating formed metallurgical bonding with the substrate.The micros tructures changed from plane crystal to dendrite,cellular dendrite,fine cellular dendrite,and then to dendrite again with the increase in the cooling rate.The crystal grew along the heat flow direction and had(111) and(200)preferred orientations when the cooling rate was 1.886 ml-min^(-1).mm^(-2).The plane crystal,dendrite and cellular dendrite were mainly composed of compounds and solid solutions with Ni,Fe and Cu,and they were surrounded by strengthening phases composed of Cr,C and B.The grain boundary of directional structure coatings showed the characteristic of regular eutectic growth,but grain boundary of remelted coating presented characteristic of divorced eutectic growth.The wear resistance of directional structure coatings is better than that of remelted coating.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2016YFE0111400)the Program on Key Research Project of Gansu Province(No.17YF1WA159)the National High-end Foreign Experts Program of China(No.GTD20156200088)
文摘By mixing preheated high-aluminum bronze powders with different amounts of Al_2O_3 powder, a low-pressure cold-sprayed coating was prepared and sprayed onto a Cr12MoV steel substrate. The hardness of the coating and the bonding strength between the coating and the substrate were tested with a HV-1000 microhardness tester and a mechanical universal testing machine. The surface microstructure, cross-section and tensile fracture surface of the coating were observed with a scanning electron microscope(SEM). Correspondingly, the influences of the preheat treatment temperature of the bronze powder and the Al_2O_3 content on the coating performance were investigated. The results indicate that the hardness of bronze powders decreased and the coating deposition rate increased after the preheating treatment of the bronze powder. The Al_2O_3 content in the mixed powders contributed to the deformation of bronze powders during the spraying process. This trend resulted in varied performance of the coating.
文摘The high-temperature oxidation behavior of arc-sprayed aluminum bronze coatings on steel substrate was studied during isothermal exposures in air at 900 ℃. The surface morphologies and interface of the coatings after isothermal oxidation at 900 ℃ for different times were observed. The experiments showed that the coatings on steel substrate were not deteriorated and the substrate was protected well, being exposed to high temperatures up to 900 ℃ . The coatings withstood more than ten times thermal shock tests without any coating separation. The thermal expansion coefficient of the coatings was measured, revealing not much difference between it and that of steel substrate. After exposure at high temperature, the coatings were still adhered to steel substrate well. Isothermal mass gain of the coatings at elevated temperature in dry air was measured by means of a thermal balance and the oxidation behavior was evaluated by oxidation kinetic curves, exhibiting the oxidation kinetics curve accorded with a parabolic law. The parabolic rate constant of the oxidation kinetic curve is 1.02×10?9 g2·cm?4·s?1 for the first 60 min and from 150 min to 2 880 min the constant is 5.1×10?12 g2·cm?4·s?1.
基金supported by the Key Research and Development Program of Zhejiang Province,China(Nos.2020C01153,2022C01139)。
文摘The cylinder block/valve plate interface is one of the most critical frictional interfaces of the swashplate-type axial piston pump.However,the poor lubrication interface caused rapid wear and high friction loss in an elastohydrodynamic lubrication system,decreasing the pump lifetime.Wear resistant bronze coatings were fabricated on 38CrMoAl substrate by Physical Vapor Deposition(PVD)and Chemical Vapor Deposition(CVD),respectively.Ball-on-disc wear tests were performed to comparatively investigate the wear behaviors of the coatings and bulk ductile iron samples.It can be found that the PVD-bronze coating exhibited better wear resistance than the other two samples.This enhanced wear resistance was attributed to the unique composite microstructure and desired mechanical strength,which could resist to mechanical shear and spallation,decreasing friction loss.The appropriate hardness of(1.33±0.07)GPa could be beneficial for enhancing its wear resistance.The PVD-bronze coating possessed a much lower and stable coefficient of friction(about 0.1)and wear rate(about 6000μm3.N-1.m-1)under the loading forces of about 100 N after 20 min.The wear mechanism was the abrasive wear.
基金financially supported by the National Natural Science Foundation of China(No.51365024)Zhejiang Provincial Natural Science Foundation of China(No.LGG19E010003)。
文摘The directional structure of Ni60/high-aluminum bronze composite coating was formed using induction remelting and forced cooling.The microstructural evolution and the characteristics of interface growth were studied.The results showed that the remelted coating formed metallurgical bonding with the substrate.The micros tructures changed from plane crystal to dendrite,cellular dendrite,fine cellular dendrite,and then to dendrite again with the increase in the cooling rate.The crystal grew along the heat flow direction and had(111) and(200)preferred orientations when the cooling rate was 1.886 ml-min^(-1).mm^(-2).The plane crystal,dendrite and cellular dendrite were mainly composed of compounds and solid solutions with Ni,Fe and Cu,and they were surrounded by strengthening phases composed of Cr,C and B.The grain boundary of directional structure coatings showed the characteristic of regular eutectic growth,but grain boundary of remelted coating presented characteristic of divorced eutectic growth.The wear resistance of directional structure coatings is better than that of remelted coating.
基金Projects (50804019, 51165021) supported by the National Natural Science Foundation of ChinaProject (0901ZTB009) supported by the Super Tutor Foundation from the Education Department of Gansu Province, China