| With the development of modern manufacturing and material technology,WC-Co cemented carbide can no longer meet the needs of the industry,and it is urgent to improve its performance and adapt to the development of technology.How to reasonably control the hardness and toughness to obtain WC-Co cemented carbide with both high hardness and high toughness is a common critical problem to be solved in this field.Considering that the interface structure has an important influence on the hardness and toughness of WC-Co cemented carbide.Electron backscatter diffraction,five parameter analysis and overlap-pole-figure analysis were used to investigated the interface characteristic distributions in the WC-Co cemented carbide samples which had been heat treated in two different ways and sintered with different additives.Based on near coincident site analysis,transmission electron microscopy analysis and mechanical properties experiments,the structural characteristics of various interfaces and their effects on the properties of WC-Co cemented carbide were discussed.The main results are as follows:Heat treatment has a significant effect on the interface characteristic distribution of WC-Co cemented carbides.For the samples treated with oil quenching after sintered at high temperature,the cobalt is mainly face-centered-cubic structure and the phase boundaries between WC and Co are mostly appear{10-10}WC/{100}Co.For the sample tempered at 800℃ and slowly cooled with protective atmosphere in the furnace,the cobalt is primarily hexagonal structure and the phase boundaries between WC and Co are mainly appear{10-10}WC/{10-10}Co.The proportion and interface matching characteristics ofΣ2 grain boundary andΣ13a grain boundary are similar,and the distribution of WC/WC grain boundary characteristics has no significant difference.The addition of additives has a significant effect on the interface characteristic distribution of WC-Co cemented carbide.The phase interface between WC and Co is mainly{0001}WC/{111}Coin the samples with transition element Cr.For the samples with transition elements Cr and Ti,the interface between WC and Co is mainly{11-20}WC/{110}Co.The interface between WC and Co is dominated by{0001}WC/{110}Cofor the samples with the addition of transition elements Cr and Mo.The ratio and interface matching characteristics ofΣ2 grain boundary andΣ13a grain boundary are similar,and the distribution of WC/WC grain boundary characteristics has no obvious difference.In addition,the proportion of special grain boundaries increased from2.7%to 4.1%compared with the samples without additives.The results of the mechanical properties and sulfuric acid corrosion resistance shows that the hardness and corrosion resistance are positively correlated with the proportion ofΣ2 grain boundaries with{10-10}/{10-10}interface matching characteristics.The fracture toughness of samples with interface characteristic distribution of FCC structure Co and WC is better than that of HCP structure Co and WC.Based on the results of performance experiments,near coincident site analysis and transmission electron microscopy analysis,the chromium element segregates at the WC/Co phase boundary to form a complexion.Σ2 grain boundary with{10-10}/{10-10}interface matching,WC/Co FCCphase boundary with{0001}WC/{100}Cointerface matching characteristics and relative rotation angle of 15°,45°and 75°,WC/Co FCCphase boundary with{0001}WC/{111}Cointerface matching characteristics and relative rotation angle of 60°play an important role in improving the hardness and toughness of WC-Co cemented carbide.The addition of the transition element Cr as a grain growth inhibitors and the rapid cooling treatment by oil quenching after high temperature sintering are conducive to the preparation of WC-Co carbide with a high proportion ofΣ2 grain boundary and a high proportion of face-centered cubic structured Co phase,and the hardness and toughness of the carbide prepared by this process are at a high level. |
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