It is reported that laser-processing is effective to repair the heat checks, which are fine shallow cracks on a surfaceof die-casting dies. In this study, the rotating bending fatigue tests have been carried out to ev...It is reported that laser-processing is effective to repair the heat checks, which are fine shallow cracks on a surfaceof die-casting dies. In this study, the rotating bending fatigue tests have been carried out to evaluate the fatiguecharacteristics of laser-processed hot working tool steel. Because test results are scattered, S-N curves are decidedbased on the evaluation of fatigue strength distribution. As a result, the fatigue strength of the laser-processedspecimens decreases remarkably in comparison with that of base metal. However, it can be recovered to almostinitial value by heat treatment at secondary hardening temperature. This procedure is also effective to decrease thescatter of fatigue strength. The laser-processing can be carried out at low cost and this method is effective for theextension of the work life of dies.展开更多
The TiC/graphene/graphite/Ti6 Al4 V composite coating was prepared by laser cladding.The microstructure and tribological behavior of the coating were studied.The in situ reaction between graphene and Ti occurred,and f...The TiC/graphene/graphite/Ti6 Al4 V composite coating was prepared by laser cladding.The microstructure and tribological behavior of the coating were studied.The in situ reaction between graphene and Ti occurred,and feathery TiC was formed.The feathery TiC was homogeneously distributed betweenα’acicular martensites which was refined with the addition of graphene.Some graphene was transformed into allotrope graphite under the laser irradiation.The TiC hard particles and the self-lubrication of graphene/graphite improved the wear resistance of composite coating.The wear rate and friction coefficient of TiC/graphene/graphite/Ti6 Al4 V composite coating decreased with the increase in sliding speed,a mechanical mixing layer(MML)was formed on the wear surface of the composite coating under the frictional heat,which protected the substrate and reduced the contact.Because of the self-lubricating properties of graphene/graphite,interlayer sliding occurred easily,which also effectively reduced friction.The wear rate of TiC/graphene/graphite/Ti6 Al4 V composite coating increased with the increase in load,but the friction coefficient decreased.The plastic deformation of subsurface layer was more serious under high load,and a stable self-lubricating MML with a protective effect was formed between the wear interfaces,which reduced the friction coefficient.With the increase in load,the wear mechanism changed from abrasive and oxidation wear to delamination,fatigue and oxidation wear.展开更多
文摘It is reported that laser-processing is effective to repair the heat checks, which are fine shallow cracks on a surfaceof die-casting dies. In this study, the rotating bending fatigue tests have been carried out to evaluate the fatiguecharacteristics of laser-processed hot working tool steel. Because test results are scattered, S-N curves are decidedbased on the evaluation of fatigue strength distribution. As a result, the fatigue strength of the laser-processedspecimens decreases remarkably in comparison with that of base metal. However, it can be recovered to almostinitial value by heat treatment at secondary hardening temperature. This procedure is also effective to decrease thescatter of fatigue strength. The laser-processing can be carried out at low cost and this method is effective for theextension of the work life of dies.
基金the National Natural Science Foundation of China(Grant Nos.51775521)the National Defense Foundation of China(No.61400040208)+4 种基金the China Postdoctoral Science Foundation(No.2019M661068)the Key Research and Development Project of Shanxi Province(No.201903D121009)the Natural Science Foundation of Shanxi Province(No.201801D221154)the Shanxi Foundation Research Projects for Application(No.201801D221234)the International Science and Technology Cooperation Program of Shanxi Province(No.201603D421024)。
文摘The TiC/graphene/graphite/Ti6 Al4 V composite coating was prepared by laser cladding.The microstructure and tribological behavior of the coating were studied.The in situ reaction between graphene and Ti occurred,and feathery TiC was formed.The feathery TiC was homogeneously distributed betweenα’acicular martensites which was refined with the addition of graphene.Some graphene was transformed into allotrope graphite under the laser irradiation.The TiC hard particles and the self-lubrication of graphene/graphite improved the wear resistance of composite coating.The wear rate and friction coefficient of TiC/graphene/graphite/Ti6 Al4 V composite coating decreased with the increase in sliding speed,a mechanical mixing layer(MML)was formed on the wear surface of the composite coating under the frictional heat,which protected the substrate and reduced the contact.Because of the self-lubricating properties of graphene/graphite,interlayer sliding occurred easily,which also effectively reduced friction.The wear rate of TiC/graphene/graphite/Ti6 Al4 V composite coating increased with the increase in load,but the friction coefficient decreased.The plastic deformation of subsurface layer was more serious under high load,and a stable self-lubricating MML with a protective effect was formed between the wear interfaces,which reduced the friction coefficient.With the increase in load,the wear mechanism changed from abrasive and oxidation wear to delamination,fatigue and oxidation wear.
