The selective laser melting(SLM) method has a great potential for fabricating injection mold with complex structure. However, the microstructure and performance of the SLM molds show significantly di erent from those ...The selective laser melting(SLM) method has a great potential for fabricating injection mold with complex structure. However, the microstructure and performance of the SLM molds show significantly di erent from those manufac?tured by traditional technologies. In this study, the microstructure, hardness and especially corrosion behavior of the samples fabricated by SLM and casting were investigated. The XRD results exhibit that the γ?Fe phase is only obtained in the SLM parts, and the α?Fe peak slightly moves to low di raction angle compared with casting counterparts. Due to the rapid cooling rate, the SLM samples have fine cellular microstructures while the casting ones have coarse grains with obvious elements segregation. Besides, the SLM samples show anisotropy, hardness of side view and top view are 48.73 and 50.31 HRC respectively, which are 20% higher than that of casting ones. Corrosion results show that the SLM samples have the better anti?corrosion resistance(in a 6% FeCl3 solution for 48 h) but the deeper corrosion pits than casting ones. Finally, the performance of the SLM molds could meet the requirement of injecting production. Moreover, the molds especially present a significant decrease(20%) of cooling time and increases of cooling uniform?ity due to the customized conformal cooling channels.展开更多
Additive manufacturing is expected to transform and upgrade the traditional foundry industry to realize the integrated manufacturing and rapid and low-cost development of high-performance components with complex shape...Additive manufacturing is expected to transform and upgrade the traditional foundry industry to realize the integrated manufacturing and rapid and low-cost development of high-performance components with complex shapes.The additive manufacturing technology commonly applied in casting mold preparation(fusible molds,sand molds/cores and ceramic cores)mainly includes selective laser sintering(SLS)and binder injection three-dimensional printing(3DP).In this work,the research status of SLS/3DP-casting processes on material preparation,equipment development,process optimization,simulation and application cases in aerospace,automotive and other fields were elaborated.Finally,the developing trends of the additive manufacturing technology in the future of foundry field are introduced,including multi-material sand molds(metal core included),ceramic core-shell integration and die-casting dies with conformal cooling runners.展开更多
The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great leachability.In this paper,the silica-based ceramic cores reinforced with ZrSiO_(4) were prepared by lase...The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great leachability.In this paper,the silica-based ceramic cores reinforced with ZrSiO_(4) were prepared by laser powder bed fusion(LPBF)combined with vacuum infiltration(VI).To enhance the infiltration effect,the pre-sintered bodies with high porosity and hydrophilicity were obtained by pre-sintering at 1100℃.Results showed that a large number of silica particles infiltrated into the pre-sintered bodies.The infiltrated silica promoted the generation of liquid phase in sintering,thereby promoting the removal of pores and the connection of grains.Nevertheless,the dispersed ZrSiO_(4) grains prevented the viscous flow of the liquid phase,thereby increasing the porosity.ZrSiO_(4) grains could hinder the propagation of cracks due to their high strength.When the addition of ZrSiO_(4) was 10 wt.%,room-temperature flexural strength of silica-based ceramic cores infiltrated with slurry S1(the mass ratio of silica sol to silica powder was 10:1)reached 17.21 MPa due to the reinforcement of sintering necks.Moreover,high-temperature flexural strength reached 13.90 MPa.Therefore,the pre-sintering process could greatly improve the mechanical properties of silica-based ceramic cores prepared by LPBF-VI technology.展开更多
Selective laser melting(SLM)tungsten(W)constantly su ered from severe cracking phenomenon due to the high melting temperature and low intrinsic ductility of W material.To address this significant issue,active ZrC nano...Selective laser melting(SLM)tungsten(W)constantly su ered from severe cracking phenomenon due to the high melting temperature and low intrinsic ductility of W material.To address this significant issue,active ZrC nanoparticles were introduced into the W matrix to form ZrC/W composites in situ by SLM to enhance the intrinsic toughness of W in this study.It mainly focused on the e ect of ZrC nanoparticle on the microstructure and cracking behavior of SLM W.Compared to SLM W,SLM ZrC/W composites showed finer equiaxed grains rather than columnar grains,because the ZrC nanoparticles provided many heterogeneous nucleation sites.Furthermore,ZrC nanoparticles could react with oxygen impurity at the grain boundaries(GBs),and then form stable ZrO2 and ZrW2O8 to purify and improve the cohesion strength of GBs.The columnar to equiaxed transition(CET)of grains and purified GBs played an important role in inhibiting the formation and propagation of the cracks in SLM W.Therefore,SLM ZrC/W composites exhibited lower crack density and higher mechanical properties compared to SLM W.This study provides a novel approach for suppressing the cracking susceptibility of SLM W.展开更多
基金National Natural Science Foundation of China(Grant No.51605176)National Hi-tech R&D Program of China(863 Program,Grant No.2015AA042501)+3 种基金Hubei Provincial Natural Science Foundation of China(Grant No.2018CFB502)Guangdong Provincial Technology Major Project of China(Grant No.2017B090911007)State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology(Grant No.P2019-006)Engineering Research Center of Rock-Soil Drilling&Excavation and Protection,Ministry of Education(Grant No.201804)
文摘The selective laser melting(SLM) method has a great potential for fabricating injection mold with complex structure. However, the microstructure and performance of the SLM molds show significantly di erent from those manufac?tured by traditional technologies. In this study, the microstructure, hardness and especially corrosion behavior of the samples fabricated by SLM and casting were investigated. The XRD results exhibit that the γ?Fe phase is only obtained in the SLM parts, and the α?Fe peak slightly moves to low di raction angle compared with casting counterparts. Due to the rapid cooling rate, the SLM samples have fine cellular microstructures while the casting ones have coarse grains with obvious elements segregation. Besides, the SLM samples show anisotropy, hardness of side view and top view are 48.73 and 50.31 HRC respectively, which are 20% higher than that of casting ones. Corrosion results show that the SLM samples have the better anti?corrosion resistance(in a 6% FeCl3 solution for 48 h) but the deeper corrosion pits than casting ones. Finally, the performance of the SLM molds could meet the requirement of injecting production. Moreover, the molds especially present a significant decrease(20%) of cooling time and increases of cooling uniform?ity due to the customized conformal cooling channels.
基金the Principle and Method of Integrated Laser 3D Printing of Metal Core-Variable Area Performance Complex Sand Mold(Grant No.U1808216)the Aero Engine and Gas Turbine Major Special Fundamental Research Fund Project(2017-Ⅶ-0008-0102)。
文摘Additive manufacturing is expected to transform and upgrade the traditional foundry industry to realize the integrated manufacturing and rapid and low-cost development of high-performance components with complex shapes.The additive manufacturing technology commonly applied in casting mold preparation(fusible molds,sand molds/cores and ceramic cores)mainly includes selective laser sintering(SLS)and binder injection three-dimensional printing(3DP).In this work,the research status of SLS/3DP-casting processes on material preparation,equipment development,process optimization,simulation and application cases in aerospace,automotive and other fields were elaborated.Finally,the developing trends of the additive manufacturing technology in the future of foundry field are introduced,including multi-material sand molds(metal core included),ceramic core-shell integration and die-casting dies with conformal cooling runners.
基金financially supported by National Science and Technology Major Project(No.2017-Ⅶ−0008-0102)National Nat-ural Science Foundation of China(No.51975230)Fundamental Research Funds for the Central Universities(Nos.2019kfyXMPY020,2020kfyFPZX003,2018KFYYXJJ030 and 2019kfyXKJC011)。
文摘The silica-based ceramic core has attracted much attention in the preparation of hollow blades due to its great leachability.In this paper,the silica-based ceramic cores reinforced with ZrSiO_(4) were prepared by laser powder bed fusion(LPBF)combined with vacuum infiltration(VI).To enhance the infiltration effect,the pre-sintered bodies with high porosity and hydrophilicity were obtained by pre-sintering at 1100℃.Results showed that a large number of silica particles infiltrated into the pre-sintered bodies.The infiltrated silica promoted the generation of liquid phase in sintering,thereby promoting the removal of pores and the connection of grains.Nevertheless,the dispersed ZrSiO_(4) grains prevented the viscous flow of the liquid phase,thereby increasing the porosity.ZrSiO_(4) grains could hinder the propagation of cracks due to their high strength.When the addition of ZrSiO_(4) was 10 wt.%,room-temperature flexural strength of silica-based ceramic cores infiltrated with slurry S1(the mass ratio of silica sol to silica powder was 10:1)reached 17.21 MPa due to the reinforcement of sintering necks.Moreover,high-temperature flexural strength reached 13.90 MPa.Therefore,the pre-sintering process could greatly improve the mechanical properties of silica-based ceramic cores prepared by LPBF-VI technology.
基金financially supported by the National Natural Science Foundation of China(Grant No.U1808216)Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(Grant No.26420190002)+1 种基金Natural Science Foundation of Hubei Province(Grant No.2018CFB502)State Key Laboratory of Materials Processing and Die and Mould Technology,Huazhong University of Science and Technology(Grant No.P2019-006)
文摘Selective laser melting(SLM)tungsten(W)constantly su ered from severe cracking phenomenon due to the high melting temperature and low intrinsic ductility of W material.To address this significant issue,active ZrC nanoparticles were introduced into the W matrix to form ZrC/W composites in situ by SLM to enhance the intrinsic toughness of W in this study.It mainly focused on the e ect of ZrC nanoparticle on the microstructure and cracking behavior of SLM W.Compared to SLM W,SLM ZrC/W composites showed finer equiaxed grains rather than columnar grains,because the ZrC nanoparticles provided many heterogeneous nucleation sites.Furthermore,ZrC nanoparticles could react with oxygen impurity at the grain boundaries(GBs),and then form stable ZrO2 and ZrW2O8 to purify and improve the cohesion strength of GBs.The columnar to equiaxed transition(CET)of grains and purified GBs played an important role in inhibiting the formation and propagation of the cracks in SLM W.Therefore,SLM ZrC/W composites exhibited lower crack density and higher mechanical properties compared to SLM W.This study provides a novel approach for suppressing the cracking susceptibility of SLM W.
