Papers by Keyword: WC/Co Composite Powder

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Authors: Hoo Soon Im, Jah Mahn Hur, Wan Jae Lee
Abstract: The dry-milling technique was used for mixing and crushing oxides and graphite powder to get homogeneous mixed powders. The weight ratio of ball-to-powder was 30:1 and argon gas was filled in jar. The carbon content was more 10~ 20wt% than the stoichiometric amount. The drymilling was carried for 20 hours. After milling, the mixed powders were reduced and carburized at 900~980°C for 3 hours flowing Ar gas in tube furnace. The dry-milled powders showed wide diffraction patterns of X-ray. The reactions of reduction and carburization were completed in 3 hours at 980°C. After the reactions, the mean size of WC particles was about 200 nm. The content of free carbon in WC/Co mixed powders decreased as the reaction temperature increased.
1149
Authors: Hoo Soon Im, Jah Mahn Hur, Wan Jae Lee
Abstract: Nano-sized WC particles in WC/Co composite powders were synthesized by mechanochemical method. The raw powders(WO3, Co3O4, VC, Cr3C2 and graphite) were mixed by planetary milling with ethyl alcohol for 30 hours. The compositions were WC-10 and -20 wt% Co after reduction and carburization. The powders of VC and Cr3C2 were added as the inhibitors to inhibit the formation of nano-sized WC particles. The direct reduction and carburization of the oxides with carbon were carried at 900°C for 1 to 3 hours under flowing Ar gas. The resultant powders were compacted and sintered at 1300~1360°C for 0.5 hour. The degree of the direct reduction and carburization of the mixed powders increased with the reaction time. The mean size of WC particles in WC/Co composite powders was about 16 nm, and the mean size of WC/Co composite powders was about 240 nm. In WC-10 and -20 wt% Co, the sintered compacts shrank by 16% and 24%, respectively. The mean sizes of WC in WC/Co composite powders were about 50 and 30 nm.
1177
Authors: Dong Ryoul Lee, Wan Jae Lee
Abstract: Direct reduction and carburization process was thought one of the best methods to make nano-sized WC powder. The oxide powders were mixed with graphite powder by ball milling in the compositions of WC-5,-10wt%Co. The mean size of mixed powders was about 250 nm after milling. The mixture was heated at the temperatures of 600~800°C for 5 hours in Ar. The reaction time of the reduction and carburization was decreased as heating temperatures and cobalt content increased. The mean size of WC/Co composite powders was about 260 nm after the reactions. And the mean size of WC grains in WC/Co composite powder was about 38 nm after the reaction at 800°C for 5 hours.
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