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Optimizition of Compositions and Processing Parameters and Wear Properties of Cemented Carbides YG11R Modified by Nanosized Rare Earth

Author: PengFei
Tutor: WangYou
School: Harbin Institute of Technology
Course: Materials Science
Keywords: YG11R nanosized rare earth modification orthogonal design wear property
CLC: TG135.5
Type: Master's thesis
Year: 2008
Downloads: 86
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Abstract


In this paper, for the purpose of mining for applications, utilizing the effect of small size and surface characteristics of nano-materials, nanosized rare earth（RE for short） additives were added into the traditional raw materials to modify the WC-Co cemented carbides （CC for short）. According to the nine programs which were designed by orthogonal design, nine types of cemented carbides YG11R were fabricated by vacuum sintering.The microstructures of the samples were observed and researched by scanning electron microscope （SEM）, transmission electron microscope （TEM）, X-ray diffraction analysis （XRD）. Hardness、transverse rupture strength、fracture toughness、impact toughness、wear resistance、coercive force and cobalt magnetic were also tested. The influence of sintering tempreture、WC grain size、ball milling time and additives content on mechanical properties were researched by orthogonal analysis. The best program is: the sintering temperature of 1450℃, the WC diameter of 11μm, the milling time of 28 h, the content of the additives of 0.05%0.15%.XRD analysis showed that only WC and Co diffraction peaks can be found, there is no diffraction peak of the lacking carbon phase. The scanning results of elements distribution showed that the WC grain, Co and the RE were distributed evenly, additionally, there is no obvious abnormal coarse particles. TEM observation and analysis of micro-structure showed that there existed someα-Co and a small amount ofε-Co with the structure of dislocation in cemented carbide fabricated.SEM fracture surface observations showed that the main fracture mechanism of CCZ7 is intercrystalline fracture, while the dominent fracture mechanism of CCZ8 and Z9 is transgranular fracture.In the nine types of the samples, the hardness of CCZ4 and CCZ7 is the highest, with the value HRA89.0. The transverse rupture strength of CCZ5 is up to 2548 MPa. The fracture toughness of CCZ8 is the highest, with the value 20.48MPa·m1/2. The impact toughness of CCZ1 is the highest, with the impact energy 4.44 J. With quartz sand as the abrasive, impact abrasive wear is used to research the mining CC’s wear performance. According to the test results, the wear property of CCZ7 in the nine types of the samples is the best. The observation of the worn surface morphology showed the dominant mechanism of impact abrasive wear with quartz sand as the abrasive is the fracture, fragmentation and falling off of WC grains.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Special mechanical properties of alloy > Hard alloy
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