The strength and thermal conductivity of compacted graphite iron(CGI)are crucial performance indicators in its engineering application.The presence of graphite in CGI significantly influences the two properties.In the...The strength and thermal conductivity of compacted graphite iron(CGI)are crucial performance indicators in its engineering application.The presence of graphite in CGI significantly influences the two properties.In the previous studies,graphite in CGI was often described using two-dimensional(2D)morphology.In this study,the three-dimensional(3D)size,shape,and distribution of graphite in CGI were analyzed using X-ray tomography.Based on this,a new method is introduced to calculate the 3D vermicularity and compare it with the 2D vermicularity in terms of tensile properties and thermal conductivity.The results demonstrate that vermicular graphite exhibits greater connectivity in 3D observation compared to 2D observation.Therefore,the calculation method of 3D vermicularity is determined by considering the surface area and volume of the connected graphite.Then a linear relationship between 3 and 2D vermicularity has been observed.By comparing the correlation coefficient,it has been found that the 3D vermicularity offers a more accurate method to establish the relationship among graphite morphology,thermal conductivity and tensile property of CGI.展开更多
High-temperature tribology,which is often involved during hot metal forming,is controlled via oxidation on a rubbing surface.However,for high chromium stainless steel(ST),where oxidation is strongly inhibited,the effe...High-temperature tribology,which is often involved during hot metal forming,is controlled via oxidation on a rubbing surface.However,for high chromium stainless steel(ST),where oxidation is strongly inhibited,the effect of counterface materials on tribological behavior is yet to be elucidated.In this study,the effects of counterfaces on the tribological behavior of 253MA ST and mild steel(MS)are investigated via a ball-on-disc test at 900°C using a 20 N load.The results reveal that high-speed steel(HSS)experiences severe abrasive wear with MS and causes severe sticking problems with ST.Si3N4 and SiC present substantially stronger abrasive wear resistance than HSS with MS,and the friction coefficients are dependent on the type of ceramic.Both ceramics can facilitate the establishment of a thick tribo-oxide layer(>3μm)on ST to prevent sticking;however,this is accompanied by severe pull-out and fracture wear.The effects of the counterface on the mechanical properties of the tribo-oxide layer,near-surface transformation,and the responses of the tribo-oxide layer to friction and wear are discussed.This study contributes to the understanding of interfacial tribological behaviors when different types of tools are used on MS and ST.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)under Grant.Nos.51871224 and 52130002the Guangdong Basic and Applied Basic Research Foundation(2021A1515010890).
文摘The strength and thermal conductivity of compacted graphite iron(CGI)are crucial performance indicators in its engineering application.The presence of graphite in CGI significantly influences the two properties.In the previous studies,graphite in CGI was often described using two-dimensional(2D)morphology.In this study,the three-dimensional(3D)size,shape,and distribution of graphite in CGI were analyzed using X-ray tomography.Based on this,a new method is introduced to calculate the 3D vermicularity and compare it with the 2D vermicularity in terms of tensile properties and thermal conductivity.The results demonstrate that vermicular graphite exhibits greater connectivity in 3D observation compared to 2D observation.Therefore,the calculation method of 3D vermicularity is determined by considering the surface area and volume of the connected graphite.Then a linear relationship between 3 and 2D vermicularity has been observed.By comparing the correlation coefficient,it has been found that the 3D vermicularity offers a more accurate method to establish the relationship among graphite morphology,thermal conductivity and tensile property of CGI.
基金This work is financially supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.51905213)the Natural Science Foundation of Guangdong(906055014066)the Fundamental Research Funds for the Central Universities(No.21619337).
文摘High-temperature tribology,which is often involved during hot metal forming,is controlled via oxidation on a rubbing surface.However,for high chromium stainless steel(ST),where oxidation is strongly inhibited,the effect of counterface materials on tribological behavior is yet to be elucidated.In this study,the effects of counterfaces on the tribological behavior of 253MA ST and mild steel(MS)are investigated via a ball-on-disc test at 900°C using a 20 N load.The results reveal that high-speed steel(HSS)experiences severe abrasive wear with MS and causes severe sticking problems with ST.Si3N4 and SiC present substantially stronger abrasive wear resistance than HSS with MS,and the friction coefficients are dependent on the type of ceramic.Both ceramics can facilitate the establishment of a thick tribo-oxide layer(>3μm)on ST to prevent sticking;however,this is accompanied by severe pull-out and fracture wear.The effects of the counterface on the mechanical properties of the tribo-oxide layer,near-surface transformation,and the responses of the tribo-oxide layer to friction and wear are discussed.This study contributes to the understanding of interfacial tribological behaviors when different types of tools are used on MS and ST.
