Composite powders of nanocrystalline WC-10Co （15wt%）,Y2O3 （8mol%） stabilized nanocrystalline ZrO2 （30wt%）,industrial cobalt powder （4.5wt%） and submicron Al2O3 （55wt%） composite powders were fabricated by hi...Composite powders of nanocrystalline WC-10Co （15wt%）,Y2O3 （8mol%） stabilized nanocrystalline ZrO2 （30wt%）,industrial cobalt powder （4.5wt%） and submicron Al2O3 （55wt%） composite powders were fabricated by high-energy ball-milling process.The nanocomposite powders were consolidated by microwave sintering process at temperature ranged 1300℃-1550℃ for 15min,respectively.The optimum consolidation conditions,such as temperature,were researched during microwave sintering process.Vickers Hardness of the consolidated cermets was measured by using a Vickers indentation test,and density of specimens was also determined by Archimedes＇ principle.Microwave sintering process could not only increase the density of Al2O3-ZrO2-WC-Co cermets and reduce the porosity,but also inhibit abnormal grain growth.展开更多
To improve the mechanical properties of WC-Al2O3 composites, the effects of trace amount of CeO2 additives on the microstructure and mechanical properties of the WC-Al2O3 composites prepared by hot pressing were inves...To improve the mechanical properties of WC-Al2O3 composites, the effects of trace amount of CeO2 additives on the microstructure and mechanical properties of the WC-Al2O3 composites prepared by hot pressing were investigated. The results revealed that the WC-Al2O3 composites doped with 0.1% CeOz possessed refined microstructure and enhanced mechanical properties compared with that of the undoped WC-Al2O3composites. Trace CeO2 suppressed the decarburization of WC, promoted the microstructural refinement, and improved the interface coherence of the WC matrix and Al2O3. When 0.1% CeO2 was added to the WC-Al2O3 composites, the effect of CeO2 resulted in the achievement of a relative density of 98.82% with an excellent Vickers hardness of 16.89 GPa, combining a fracture toughness of 9.85 MPa. m1/2 with an acceptable flexural strength of 1 024.05 MPa.展开更多
A facile and cheap method for the fabrication of WC-Al2O3composite powder was proposed.Thermodynamic calculations indicate that aluminothermic reduction of WO3in WO3:xAl:(4-1.5x)C mixture is accompanied by a great dea...A facile and cheap method for the fabrication of WC-Al2O3composite powder was proposed.Thermodynamic calculations indicate that aluminothermic reduction of WO3in WO3:xAl:(4-1.5x)C mixture is accompanied by a great deal of heat,so carbothermic reduction reaction(endothermic)becomes activated in the system.By substitution of aluminum with carbon,the formation of unwanted W2C phase can be prevented because of less thermodynamic stability at lower temperatures.For the verification of the proposed reaction mechanism,various WO3:xAl:(4-1.5x)C mixtures(1.1≤x≤2)were heat-treated in a domestic microwave oven.The results showed that the type of reaction is self-propagating high temperature synthesis(SHS)when1.4≤x≤2.Lower amount of Al in WO3:xAl:(4-1.5x)C mixtures results in a higher formation of WC.A W2C-free WC-Al2O3composite was obtained by continuation of microwave heating in an isolated atmosphere,after the occurrence of SHS reaction in a mixture containing1.4mol of Al.Results also showed that when x≤1.3,type of reaction becomes gradual,which in turn brings about the incompleteness reaction and residue of initial reagents.展开更多
基金Funded by the Youth Science Plan for Light of the Morning Sun of Wuhan City (200750731270)
文摘Composite powders of nanocrystalline WC-10Co （15wt%）,Y2O3 （8mol%） stabilized nanocrystalline ZrO2 （30wt%）,industrial cobalt powder （4.5wt%） and submicron Al2O3 （55wt%） composite powders were fabricated by high-energy ball-milling process.The nanocomposite powders were consolidated by microwave sintering process at temperature ranged 1300℃-1550℃ for 15min,respectively.The optimum consolidation conditions,such as temperature,were researched during microwave sintering process.Vickers Hardness of the consolidated cermets was measured by using a Vickers indentation test,and density of specimens was also determined by Archimedes＇ principle.Microwave sintering process could not only increase the density of Al2O3-ZrO2-WC-Co cermets and reduce the porosity,but also inhibit abnormal grain growth.
文摘To improve the mechanical properties of WC-Al2O3 composites, the effects of trace amount of CeO2 additives on the microstructure and mechanical properties of the WC-Al2O3 composites prepared by hot pressing were investigated. The results revealed that the WC-Al2O3 composites doped with 0.1% CeOz possessed refined microstructure and enhanced mechanical properties compared with that of the undoped WC-Al2O3composites. Trace CeO2 suppressed the decarburization of WC, promoted the microstructural refinement, and improved the interface coherence of the WC matrix and Al2O3. When 0.1% CeO2 was added to the WC-Al2O3 composites, the effect of CeO2 resulted in the achievement of a relative density of 98.82% with an excellent Vickers hardness of 16.89 GPa, combining a fracture toughness of 9.85 MPa. m1/2 with an acceptable flexural strength of 1 024.05 MPa.
文摘A facile and cheap method for the fabrication of WC-Al2O3composite powder was proposed.Thermodynamic calculations indicate that aluminothermic reduction of WO3in WO3:xAl:(4-1.5x)C mixture is accompanied by a great deal of heat,so carbothermic reduction reaction(endothermic)becomes activated in the system.By substitution of aluminum with carbon,the formation of unwanted W2C phase can be prevented because of less thermodynamic stability at lower temperatures.For the verification of the proposed reaction mechanism,various WO3:xAl:(4-1.5x)C mixtures(1.1≤x≤2)were heat-treated in a domestic microwave oven.The results showed that the type of reaction is self-propagating high temperature synthesis(SHS)when1.4≤x≤2.Lower amount of Al in WO3:xAl:(4-1.5x)C mixtures results in a higher formation of WC.A W2C-free WC-Al2O3composite was obtained by continuation of microwave heating in an isolated atmosphere,after the occurrence of SHS reaction in a mixture containing1.4mol of Al.Results also showed that when x≤1.3,type of reaction becomes gradual,which in turn brings about the incompleteness reaction and residue of initial reagents.
