The design freedom of powder bed fusion process selective laser melting(SLM)enables flexibility to manufacture customized,geometrically complex medical implants directly from the CAD models.Cobased alloys have adequat...The design freedom of powder bed fusion process selective laser melting(SLM)enables flexibility to manufacture customized,geometrically complex medical implants directly from the CAD models.Cobased alloys have adequate wear and corrosion resistance,fatigue strength,and biocompatibility,which enables the alloys to be widely used in medical devices.This work aims to investigate the evolution of microstructures and their influence on tribological property of CoCrMo alloy processed by SLM and aging heat treatment.The results showed that very weak<110>texture along the building direction and microsegregation along cellular boundaries were produced.The presence of high residual stress and fine cellular dendrite structure has a pronounced hardening effect on the as-SLM and aging-treated alloys at moderate temperatures.Furthermore,the hexagonalεphase transformed from theγmatrix during SLM became significant after subsequent aging at moderate temperatures,which further increased the nanohardness and scratch resistance.High temperature(1150℃)heating caused homogenized recrystallization microstructure free of residual stress andεphase,which sharply decreased the hardness and scratch resistance.The material parallel to the building direction exhibited improved tribological property in both SLMed and aging-treated alloy than that of the material perpendicular to the building direction.The anisotropy in frictional performance may be considered when designing CoCrMo dental implants using laser additive manufacturing.展开更多
In order to improve the corrosion resistance of carbon steel,Hastelloy coatings were prepared on E235steel substrate by ahigh power diode laser with laser scanning speeds of6and12mm/s,respectively.The interface betwee...In order to improve the corrosion resistance of carbon steel,Hastelloy coatings were prepared on E235steel substrate by ahigh power diode laser with laser scanning speeds of6and12mm/s,respectively.The interface between the coating and substratewas firstly exposed by dissolving off the substrate.Its microstructure,composition and mechanical properties were systemicallystudied.Special“edges”along the grain boundary were found at coating/substrate interface.These“edges”consisted of intergranularcorrosion area and real grain boundary.The interface of coating mainly displayed austenite structure ascribed to the rapidsolidification as well as the dilution of Ni during preparation.Additionally,Hastelloy coating and its interface prepared at the speedof12mm/s showed higher hardness than that prepared at the speed of6mm/s.Grain boundaries had higher friction coefficient thangrains at both coating/substrate interfaces.Moreover,the interface at higher laser scanning speed exhibited smaller grains,lowerdilution rates of Ni and Fe as well as a better tribological property.展开更多
The microstructure and nano-tribological properties of 316 austenitic stainless steel have been investigated by using the in situ nano-mechanical testing system Tribolndenter, in which six different normal forces were...The microstructure and nano-tribological properties of 316 austenitic stainless steel have been investigated by using the in situ nano-mechanical testing system Tribolndenter, in which six different normal forces were chosen to make a scratch and indentation. The results show that the contact depth of the indentation increases with the normal force and material is piled up on the edge of the indentation as plastic distortion. The stable nano-hardness and the reduced modulus of 316 austenitic stainless steel are approximately 6 GPa and 160 GPa, respectively. The friction coefficients of 316 stainless steel with conic-type diamond tip have a typical value of about 0.13, 0.15, 0.17, 0.19, 0.22 and 0.25 when the normal forces are kept at 500 μN, 1000 μN, 1500 μN, 2000 μN, 2500 μN and 3000 μN, revealing an increasing trend with the normal forces. The increase of the friction coefficient in the unloading segment may result from the adhesion force caused by the material piled up.展开更多
基金the Key R&D Plan of the Ministry of Science and Technology(No.2018YFB1105900)the Shandong Province Key R&D Project(No.2018GGX103017)the Zibo City and SDUT Integration Project(No.2018ZBXC154)。
文摘The design freedom of powder bed fusion process selective laser melting(SLM)enables flexibility to manufacture customized,geometrically complex medical implants directly from the CAD models.Cobased alloys have adequate wear and corrosion resistance,fatigue strength,and biocompatibility,which enables the alloys to be widely used in medical devices.This work aims to investigate the evolution of microstructures and their influence on tribological property of CoCrMo alloy processed by SLM and aging heat treatment.The results showed that very weak<110>texture along the building direction and microsegregation along cellular boundaries were produced.The presence of high residual stress and fine cellular dendrite structure has a pronounced hardening effect on the as-SLM and aging-treated alloys at moderate temperatures.Furthermore,the hexagonalεphase transformed from theγmatrix during SLM became significant after subsequent aging at moderate temperatures,which further increased the nanohardness and scratch resistance.High temperature(1150℃)heating caused homogenized recrystallization microstructure free of residual stress andεphase,which sharply decreased the hardness and scratch resistance.The material parallel to the building direction exhibited improved tribological property in both SLMed and aging-treated alloy than that of the material perpendicular to the building direction.The anisotropy in frictional performance may be considered when designing CoCrMo dental implants using laser additive manufacturing.
基金Project supported by the New Staff Research Start-up Fund and the Innovation Fund(School of Materials Science and Engineering) of Southwest Petroleum University,China
文摘In order to improve the corrosion resistance of carbon steel,Hastelloy coatings were prepared on E235steel substrate by ahigh power diode laser with laser scanning speeds of6and12mm/s,respectively.The interface between the coating and substratewas firstly exposed by dissolving off the substrate.Its microstructure,composition and mechanical properties were systemicallystudied.Special“edges”along the grain boundary were found at coating/substrate interface.These“edges”consisted of intergranularcorrosion area and real grain boundary.The interface of coating mainly displayed austenite structure ascribed to the rapidsolidification as well as the dilution of Ni during preparation.Additionally,Hastelloy coating and its interface prepared at the speedof12mm/s showed higher hardness than that prepared at the speed of6mm/s.Grain boundaries had higher friction coefficient thangrains at both coating/substrate interfaces.Moreover,the interface at higher laser scanning speed exhibited smaller grains,lowerdilution rates of Ni and Fe as well as a better tribological property.
基金Project 50535050 supported by National Natural Science Foundation of China
文摘The microstructure and nano-tribological properties of 316 austenitic stainless steel have been investigated by using the in situ nano-mechanical testing system Tribolndenter, in which six different normal forces were chosen to make a scratch and indentation. The results show that the contact depth of the indentation increases with the normal force and material is piled up on the edge of the indentation as plastic distortion. The stable nano-hardness and the reduced modulus of 316 austenitic stainless steel are approximately 6 GPa and 160 GPa, respectively. The friction coefficients of 316 stainless steel with conic-type diamond tip have a typical value of about 0.13, 0.15, 0.17, 0.19, 0.22 and 0.25 when the normal forces are kept at 500 μN, 1000 μN, 1500 μN, 2000 μN, 2500 μN and 3000 μN, revealing an increasing trend with the normal forces. The increase of the friction coefficient in the unloading segment may result from the adhesion force caused by the material piled up.
