In the paper, the effect of niobium addition on the microstructure, mechanical properties and wear resistance of high chromium cast iron has been studied. The results show that the microstructure of the heattreated al...In the paper, the effect of niobium addition on the microstructure, mechanical properties and wear resistance of high chromium cast iron has been studied. The results show that the microstructure of the heattreated alloys is composed of M7C3 and M23C6 types primary carbide, eutectic carbide, secondary carbide and a matrix of martensite and retained austenite. NbC particles appear both inside and on the edge of the primary carbides. The hardness of the studied alloys maintains around 66 HRC, not significantly affected by the Nb content within the selected range of 0.48%-0.74%. The impact toughness of the alloys increases with increasing niobium content. The wear resistance of the specimens presents little variation in spite of the increase of Nb content under a light load of 40 N. However, when heavier loads of 70 and 100 N are applied, the wear resistance increases with increasing Nb content.展开更多
Rolling process based on the plastic deformation as a surface strengthening treatment was employed,aiming to improve the wear resistance ability and functional performance of the high carbon equivalent gray cast iron(...Rolling process based on the plastic deformation as a surface strengthening treatment was employed,aiming to improve the wear resistance ability and functional performance of the high carbon equivalent gray cast iron(HCEGCI).The microstructures and tribological performance of the untreated and rolled samples were characterized.In addition,the wear mechanism of HCEGCI samples was also studied via pin-on-disc tests.The experimental results show that the as-rolled samples possess the structure-refined layer of 15μm and work-hardened layer of 0.13 mm.In comparison with the surface hardness of untreated samples,the surface hardness of as-rolled samples increases by 84.6%(from 240HV0.1 to 443HV0.1)and the residual compressive stresses existed within the range of 0.2 mm.The wear rates of as-rolled samples were decreased by 38.4%,37.5%,and 44.4%under different loads of 5 N,10 N,and 15 N,respectively.The wear characteristics of the untreated samples mainly exhibit the peeling wear coupled with partial adhesive and abrasive wear.However,as for the as-rolled samples,the adhesive wear was limited by the structure-refined layer and the micro-crack propagation was controlled by the work-hardened layer.Therefore,the wear resistance of as-rolled samples can be improved significantly due to the low wearing degree of the friction contact zone.展开更多
In the present research, high chromium cast irons(HCCIs) were prepared using the lost foam casting(LFC) process. To improve the wear resistance of the high chromium cast irons(HCCIs), mechanical vibration was employed...In the present research, high chromium cast irons(HCCIs) were prepared using the lost foam casting(LFC) process. To improve the wear resistance of the high chromium cast irons(HCCIs), mechanical vibration was employed during the solidification of the HCCIs. The effects of vibration frequency on the microstructure and performance of the HCCIs under as-cast, as-quenched and as-tempered conditions were investigated. The results indicated that the microstructures of the LFC-produced HCCIs were refined due to the introduction of mechanical vibration, and the hardness was improved compared to that of the alloy without vibration. However, only a slight improvement in hardness was found in spite of the increase of vibration frequency. In contrast, the impact toughness of the as-tempered HCCIs increased with an increase in the vibration frequency. In addition, the wear resistance of the HCCIs was improved as a result of the introduction of vibration and increased with an increase in the vibration frequency.展开更多
In the current study,an as-cast 26%Cr high chromium cast iron(HCCI)alloy was subjected to dry-sliding linear wear tests,under different loads.The loads were selected based on analytically computing the critical load(P...In the current study,an as-cast 26%Cr high chromium cast iron(HCCI)alloy was subjected to dry-sliding linear wear tests,under different loads.The loads were selected based on analytically computing the critical load(PC)i.e.,the load necessary to induce plastic deformation.The PC was calculated to be 15 N and accordingly,a sub-critical load(5 N)and an over-critical load(20 N)were chosen.The influence of increasing the load during the wear test was investigated in terms of the matrix microstructural behaviour and its ability to support the surrounding carbides.The morphological aspects of the wear tracks,and the deformed matrix microstructure adjacent and underneath the track was analysed by confocal laser scanning microscope(CLSM)and scanning electron microscope(SEM),respectively.No evidence of plastic deformation of the matrix was observed below PC.On the contrary,at loads equal to and higher than PC,the austenitic matrix plastically deformed as evidenced by the presence of slip bands.Electron backscattered diffraction(EBSD)measurements in terms of grain reference orientation deviation,and micro-Vickers hardness of the austenitic matrix indicated a deformation depth of about 40μm at the maximum applied load of 20 N.The active wear mechanisms during sliding were a combination of both adhesive and abrasive wear,although increasing the load shifted the dominant mechanism towards abrasion.This was primarily attributable to the increased propensity for carbide cracking and fracturing,combined with the inability of the hardened austenitic matrix surface and sub-surface to adequately support the broken carbide fragments.Moreover,the shift in the dominant wear mechanism was also reflected in the wear volume and subsequently,the wear rate.展开更多
基金financially supported by the Science and Technology Plan Project of Guangdong Province(Nos.2010A080407002,2011A080802003,2011A091000035,2012B090600030)the Fundamental Research Funds for the Central Universities(No.21612105)
文摘In the paper, the effect of niobium addition on the microstructure, mechanical properties and wear resistance of high chromium cast iron has been studied. The results show that the microstructure of the heattreated alloys is composed of M7C3 and M23C6 types primary carbide, eutectic carbide, secondary carbide and a matrix of martensite and retained austenite. NbC particles appear both inside and on the edge of the primary carbides. The hardness of the studied alloys maintains around 66 HRC, not significantly affected by the Nb content within the selected range of 0.48%-0.74%. The impact toughness of the alloys increases with increasing niobium content. The wear resistance of the specimens presents little variation in spite of the increase of Nb content under a light load of 40 N. However, when heavier loads of 70 and 100 N are applied, the wear resistance increases with increasing Nb content.
基金Funded by the National Natural Science Foundation of China(No.51872254)the Yangzhou Hanjiang District Science and Technology Plan Project of China(No.HJM2019006)。
文摘Rolling process based on the plastic deformation as a surface strengthening treatment was employed,aiming to improve the wear resistance ability and functional performance of the high carbon equivalent gray cast iron(HCEGCI).The microstructures and tribological performance of the untreated and rolled samples were characterized.In addition,the wear mechanism of HCEGCI samples was also studied via pin-on-disc tests.The experimental results show that the as-rolled samples possess the structure-refined layer of 15μm and work-hardened layer of 0.13 mm.In comparison with the surface hardness of untreated samples,the surface hardness of as-rolled samples increases by 84.6%(from 240HV0.1 to 443HV0.1)and the residual compressive stresses existed within the range of 0.2 mm.The wear rates of as-rolled samples were decreased by 38.4%,37.5%,and 44.4%under different loads of 5 N,10 N,and 15 N,respectively.The wear characteristics of the untreated samples mainly exhibit the peeling wear coupled with partial adhesive and abrasive wear.However,as for the as-rolled samples,the adhesive wear was limited by the structure-refined layer and the micro-crack propagation was controlled by the work-hardened layer.Therefore,the wear resistance of as-rolled samples can be improved significantly due to the low wearing degree of the friction contact zone.
基金supported by the Science and Technology Plan Project of Guangdong province,China(2015B090926012,2014B090901001034,2014YT02C036,2013B090500106,2013CX/G18)the Scientific Research and Innovation Project of Jinan University(No.21615437)
文摘In the present research, high chromium cast irons(HCCIs) were prepared using the lost foam casting(LFC) process. To improve the wear resistance of the high chromium cast irons(HCCIs), mechanical vibration was employed during the solidification of the HCCIs. The effects of vibration frequency on the microstructure and performance of the HCCIs under as-cast, as-quenched and as-tempered conditions were investigated. The results indicated that the microstructures of the LFC-produced HCCIs were refined due to the introduction of mechanical vibration, and the hardness was improved compared to that of the alloy without vibration. However, only a slight improvement in hardness was found in spite of the increase of vibration frequency. In contrast, the impact toughness of the as-tempered HCCIs increased with an increase in the vibration frequency. In addition, the wear resistance of the HCCIs was improved as a result of the introduction of vibration and increased with an increase in the vibration frequency.
基金The present work is supported by funding from the Deutsche Forschungsgemeinschaft(DFG,project:GU 2102/2-1).
文摘In the current study,an as-cast 26%Cr high chromium cast iron(HCCI)alloy was subjected to dry-sliding linear wear tests,under different loads.The loads were selected based on analytically computing the critical load(PC)i.e.,the load necessary to induce plastic deformation.The PC was calculated to be 15 N and accordingly,a sub-critical load(5 N)and an over-critical load(20 N)were chosen.The influence of increasing the load during the wear test was investigated in terms of the matrix microstructural behaviour and its ability to support the surrounding carbides.The morphological aspects of the wear tracks,and the deformed matrix microstructure adjacent and underneath the track was analysed by confocal laser scanning microscope(CLSM)and scanning electron microscope(SEM),respectively.No evidence of plastic deformation of the matrix was observed below PC.On the contrary,at loads equal to and higher than PC,the austenitic matrix plastically deformed as evidenced by the presence of slip bands.Electron backscattered diffraction(EBSD)measurements in terms of grain reference orientation deviation,and micro-Vickers hardness of the austenitic matrix indicated a deformation depth of about 40μm at the maximum applied load of 20 N.The active wear mechanisms during sliding were a combination of both adhesive and abrasive wear,although increasing the load shifted the dominant mechanism towards abrasion.This was primarily attributable to the increased propensity for carbide cracking and fracturing,combined with the inability of the hardened austenitic matrix surface and sub-surface to adequately support the broken carbide fragments.Moreover,the shift in the dominant wear mechanism was also reflected in the wear volume and subsequently,the wear rate.
