Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-ro...Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and warships.This paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)alloys.Morphological analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values better.Tribological analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze samples.The hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal bronze.Further,the grain size was approximately 30%finer for spinodal bronze when compared with regular bronze.When the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal increase.There was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze samples.These results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys.展开更多
Quenching Oils are comprised mostly of mineral oil as major component, but mineral oil alone result in lower cooling performance. Therefore, various additives are formulated as required for each particular case. Cooli...Quenching Oils are comprised mostly of mineral oil as major component, but mineral oil alone result in lower cooling performance. Therefore, various additives are formulated as required for each particular case. Cooling curves of mineral oil as determined by JIS method can be divided into three stages, vapor film stage, boiling stage and convection stage. And there are many types of additives used for quenching oil, one effective to shorten vapor film stage and another to shift boiling stage toward lower temperature side. As rapid quenching required temperature range for particular steel varies pending on its shape of CCT curve"1, it is possible to provide higher quench hardening performance using quenching oil formulated of adequate additives.展开更多
The grain growth retardation mechanism and the effect of cooling rate on VC-doped WC–Co cemented carbides were investigated in this work.WC–30Co and WC–30Co–VC were prepared by powder metallurgy,liquid-phase sinte...The grain growth retardation mechanism and the effect of cooling rate on VC-doped WC–Co cemented carbides were investigated in this work.WC–30Co and WC–30Co–VC were prepared by powder metallurgy,liquid-phase sintering at 1400 ℃ and followed by water quenching（[150 ℃/s） or furnace cooling（＊0.083 ℃/s）.Based on the results of electron probe microanalysis（EPMA）,we found that WC concentration in the Co binder was independent of VC doping during liquid-phase sintering,hence barely contributing to the retardation of WC grain growth.In contrast,the（W,V）Cx phase formed at the WC/Co interfaces played a major role in retarding WC grain growth during liquid-phase sintering.The effect of cooling rate on the morphology of（W,V）Cxwas revealed by high-resolution transmission electron microscopy（HRTEM） and energy-dispersive spectroscopy（EDS）.In the water-quenched WC–30Co–VC,（W,V）Cxprecipitates were found as thin layers at the WC/Co interfaces.In contrast,both thin layers of similar thickness and nanoparticles of（W,V）Cx were observed in the furnace-cooled counterpart.These observations listed above suggested that thin（W,V）Cxlayers were stable structures effectively suppressing the growth of WC grains and their thickness remained independent of the cooling rate.The（W,V）Cxnanoparticles,however,may be inhibited through rapid cooling,ensuring the VC-doped WC–Co cemented carbides desired toughness.展开更多
For plate quenching on a roller quenching machine, heat transfer process is investigated. According to the practical online experiment of plate center temperature, average heat transfer coefficient under different con...For plate quenching on a roller quenching machine, heat transfer process is investigated. According to the practical online experiment of plate center temperature, average heat transfer coefficient under different conditions and temperature fields are analyzed by numerical simulation. The results show that, at the water temperature of 15 ℃, the instantaneous maximum quenching cooling rate is 17.6 ℃/s for the plate of 50 mm in thickness in roller quenching process. In the temperature range of 400-850 ℃, the maximum is 12.1 ℃/s. With the plate surface temperature decreasing, surface heat transfer coefficient increases at first, and reaches the maximum value of about 15 000 W/（m^2·K）, and then decreases. The calculated heat transfer coefficients are applied to analyze plate temperature field of different thicknesses, and the difference between the calculated and measured temperature is less than 5%.展开更多
文摘Cu-Ni-Sn spinodal alloys(Spinodal bronze)are potential materials with robust applications in components associated with defence applications like bearings,propellers,bushes,and shafts of heavily loaded aircraft,off-road vehicles,and warships.This paper presents a comparative study using water,Brine solution,and SAE 40 oil as the quenching media in regular bronze(Cu-6Sn)and spinodal bronze(Cu-9Ni-6Sn)alloys.Morphological analysis was conducted by optical microscopy,transmission electron microscopy(TEM),and X-ray diffraction technique(XRD)on bronze and spinodal bronze samples immersed in the three different quenching media to understand the grain size and hardness values better.Tribological analysis was performed to analyze the effect of quenching media on the wear aspects of bronze and spinodal bronze samples.The hardness value of the brine-aged spinodal bronze samples was as high as 320 Hv,and the grain size was very low in the range of 60μm.A quantitative comparison between brine-aged regular bronze and brine-aged spinodal bronze showed that the hardness(Hv)was almost 80%higher for brine-aged spinodal bronze.Further,the grain size was approximately 30%finer for spinodal bronze when compared with regular bronze.When the load was increased in spinodal bronze samples,there was an initial dip in wear rate followed by a marginal increase.There was a steady increase in friction coefficient with a rise in load for brine-aged regular bronze and spinodal bronze samples.These results indicate that brine solution is the most effective quenching medium for cast Cu-Ni-Sn spinodal alloys.
文摘Quenching Oils are comprised mostly of mineral oil as major component, but mineral oil alone result in lower cooling performance. Therefore, various additives are formulated as required for each particular case. Cooling curves of mineral oil as determined by JIS method can be divided into three stages, vapor film stage, boiling stage and convection stage. And there are many types of additives used for quenching oil, one effective to shorten vapor film stage and another to shift boiling stage toward lower temperature side. As rapid quenching required temperature range for particular steel varies pending on its shape of CCT curve"1, it is possible to provide higher quench hardening performance using quenching oil formulated of adequate additives.
基金financially supported by the National Development and Reform Commission of China(Grant No.20121743)the National Natural Science Foundation of China(Grant No.51474244)
文摘The grain growth retardation mechanism and the effect of cooling rate on VC-doped WC–Co cemented carbides were investigated in this work.WC–30Co and WC–30Co–VC were prepared by powder metallurgy,liquid-phase sintering at 1400 ℃ and followed by water quenching（[150 ℃/s） or furnace cooling（＊0.083 ℃/s）.Based on the results of electron probe microanalysis（EPMA）,we found that WC concentration in the Co binder was independent of VC doping during liquid-phase sintering,hence barely contributing to the retardation of WC grain growth.In contrast,the（W,V）Cx phase formed at the WC/Co interfaces played a major role in retarding WC grain growth during liquid-phase sintering.The effect of cooling rate on the morphology of（W,V）Cxwas revealed by high-resolution transmission electron microscopy（HRTEM） and energy-dispersive spectroscopy（EDS）.In the water-quenched WC–30Co–VC,（W,V）Cxprecipitates were found as thin layers at the WC/Co interfaces.In contrast,both thin layers of similar thickness and nanoparticles of（W,V）Cx were observed in the furnace-cooled counterpart.These observations listed above suggested that thin（W,V）Cxlayers were stable structures effectively suppressing the growth of WC grains and their thickness remained independent of the cooling rate.The（W,V）Cxnanoparticles,however,may be inhibited through rapid cooling,ensuring the VC-doped WC–Co cemented carbides desired toughness.
基金Sponsored by National Basic Research Program(973 Program) of China(2010CB630800)
文摘For plate quenching on a roller quenching machine, heat transfer process is investigated. According to the practical online experiment of plate center temperature, average heat transfer coefficient under different conditions and temperature fields are analyzed by numerical simulation. The results show that, at the water temperature of 15 ℃, the instantaneous maximum quenching cooling rate is 17.6 ℃/s for the plate of 50 mm in thickness in roller quenching process. In the temperature range of 400-850 ℃, the maximum is 12.1 ℃/s. With the plate surface temperature decreasing, surface heat transfer coefficient increases at first, and reaches the maximum value of about 15 000 W/（m^2·K）, and then decreases. The calculated heat transfer coefficients are applied to analyze plate temperature field of different thicknesses, and the difference between the calculated and measured temperature is less than 5%.
