The W -Co compound precursor powders with an average particle sife of 60 nm were prepared by the chemical coprecipitation as the raw materials of Na2WO1 and CoCl2 and as the reagents of HCI and NH3 ?H2O. After re-duci...The W -Co compound precursor powders with an average particle sife of 60 nm were prepared by the chemical coprecipitation as the raw materials of Na2WO1 and CoCl2 and as the reagents of HCI and NH3 ?H2O. After re-ducing and carburizing the precursor powders by hydrogen gas and CO-CO 2 mixture gas. the WC-Co composite povvders ivith an average particle size of 0. 18/wi can be obtained. The purity and particle size of powders -were analysed by XRD and TEM. respectively. Meanwhile, the key factors to influ-ence the reducing and carburizing process of powders were also studied.展开更多
The WC-10%Co particulate reinforced Cu matrix composite material with a WC-Co∶Cu mass ratio of 20∶80 was successfully fabricated by selective laser sintering(SLS) process. The following optimal processing parameters...The WC-10%Co particulate reinforced Cu matrix composite material with a WC-Co∶Cu mass ratio of 20∶80 was successfully fabricated by selective laser sintering(SLS) process. The following optimal processing parameters were used: laser power of 700 W, scan speed of 0.06 m/s, scan line spacing of 0.15 mm, and powder layer thickness of 0.3 mm. The microstructure, composition, and phase of the laser processed material were investigated by scanning electron microscopy(SEM), X-ray diffraction(XRD), and energy dispersive X-ray(EDX) spectroscopy. The results show that the bonding mechanism of this process is liquid phase sintering. The Cu and Co act as the binder phase, while the WC acts as the reinforcing phase. The non-equilibrium effects induced by laser melting, such as high degrees of undercooling and high solidification rate, result in the formation of a metastable phase CoC0.25. The WC reinforcing particulates typically have three kinds of morphology. They are agglomerated and undissolved, incompletely separated and partially dissolved, separated and dissolved, which indicates that particle rearrangement acts as the dominant sintering mechanism for the larger WC, while dissolution-precipitation prevails for the smaller WC particles. Microhardness tester was used to determine the Vickers hardness across the cross-section of the laser sintered sample, with the average value being HV0.1268.5. However, the hardness varied considerably, which might be attributed to the WC segregation and the high solidification rate experienced by the molten pool.展开更多
采用电渣熔铸技术,制备了以5Cr Ni Mo模具钢为基体,WC颗粒为硬质相的钢基复合材料。利用扫描电子显微镜、冲击试验机、摩擦磨损试验机等研究了复合材料的冲击韧度、断口形貌、摩擦系数、磨损量和磨损机制。结果表明,复合材料冲击韧度值...采用电渣熔铸技术,制备了以5Cr Ni Mo模具钢为基体,WC颗粒为硬质相的钢基复合材料。利用扫描电子显微镜、冲击试验机、摩擦磨损试验机等研究了复合材料的冲击韧度、断口形貌、摩擦系数、磨损量和磨损机制。结果表明,复合材料冲击韧度值较小,断裂方式均是脆性断裂。顶部和中部试样分布着沿晶或穿晶二次裂纹,为解理断裂。尾部试样部分区域具有一些韧性特征,断口为细韧窝和部分沿晶断口。热处理后试样的耐磨性得到很大提高,在干滑动磨损条件下,试样的磨损机制主要是粘着磨损引起的表面剥落及磨屑充当第三体引起的磨粒磨损。展开更多
文摘The W -Co compound precursor powders with an average particle sife of 60 nm were prepared by the chemical coprecipitation as the raw materials of Na2WO1 and CoCl2 and as the reagents of HCI and NH3 ?H2O. After re-ducing and carburizing the precursor powders by hydrogen gas and CO-CO 2 mixture gas. the WC-Co composite povvders ivith an average particle size of 0. 18/wi can be obtained. The purity and particle size of powders -were analysed by XRD and TEM. respectively. Meanwhile, the key factors to influ-ence the reducing and carburizing process of powders were also studied.
基金Project(10276017) supported by the Joint Fund of National Natural Science Foundation of China and China Academy of Engineering Physics Project(04H52061) supported by the Aeronautical Science Foundation of China Project(S0403-061) supported by the Scientific Research Innovations Foundation of Nanjing University of Aeronautics and Astronautics
文摘The WC-10%Co particulate reinforced Cu matrix composite material with a WC-Co∶Cu mass ratio of 20∶80 was successfully fabricated by selective laser sintering(SLS) process. The following optimal processing parameters were used: laser power of 700 W, scan speed of 0.06 m/s, scan line spacing of 0.15 mm, and powder layer thickness of 0.3 mm. The microstructure, composition, and phase of the laser processed material were investigated by scanning electron microscopy(SEM), X-ray diffraction(XRD), and energy dispersive X-ray(EDX) spectroscopy. The results show that the bonding mechanism of this process is liquid phase sintering. The Cu and Co act as the binder phase, while the WC acts as the reinforcing phase. The non-equilibrium effects induced by laser melting, such as high degrees of undercooling and high solidification rate, result in the formation of a metastable phase CoC0.25. The WC reinforcing particulates typically have three kinds of morphology. They are agglomerated and undissolved, incompletely separated and partially dissolved, separated and dissolved, which indicates that particle rearrangement acts as the dominant sintering mechanism for the larger WC, while dissolution-precipitation prevails for the smaller WC particles. Microhardness tester was used to determine the Vickers hardness across the cross-section of the laser sintered sample, with the average value being HV0.1268.5. However, the hardness varied considerably, which might be attributed to the WC segregation and the high solidification rate experienced by the molten pool.
文摘采用电渣熔铸技术,制备了以5Cr Ni Mo模具钢为基体,WC颗粒为硬质相的钢基复合材料。利用扫描电子显微镜、冲击试验机、摩擦磨损试验机等研究了复合材料的冲击韧度、断口形貌、摩擦系数、磨损量和磨损机制。结果表明,复合材料冲击韧度值较小,断裂方式均是脆性断裂。顶部和中部试样分布着沿晶或穿晶二次裂纹,为解理断裂。尾部试样部分区域具有一些韧性特征,断口为细韧窝和部分沿晶断口。热处理后试样的耐磨性得到很大提高,在干滑动磨损条件下,试样的磨损机制主要是粘着磨损引起的表面剥落及磨屑充当第三体引起的磨粒磨损。
