High Temperature Carburization
Preparation of the W+C blend is the same for this type of carburization as for the conventional type. The main difference with respect to the foregoing method is the carburization temperature ranging between 1800℃ and 2200℃. Furnace types in use are push-type graphite tube furnaces, working semicontinuously with the powder in graphite vessels, and batch-type furnaces (powder in trays) either inductively or resistance heated.
High-temperature carburized powders are usually coarse (10~50um). Sometimes, 5~10um powder is also treated that way.
At temperature≥1900℃, extentsive grain (crystallite) coarsening takes place, most likely by coalescence, yielding in WC crystallite sizes up to 50um. Smaller, average-sized powder (5~10um) can partly consist of single-crystal particles.
The push-type furnaces work in flowing hydrogen atmosphere, while in batch-type furnaces a reduced pressure hydrogen atmosphere is commonly used. In case of batch carburization and especially for coarse powder, it is advantageous to precarburize the material first at 1600℃ under flowing hydrogen, then to crush and blend it, and finally to carburize at high temperature. The precarburization is mainly a cleaning step, and the subsequent crushing and blending results in an improved carbon distribution.
The percentage of high-temperature carburized WC is low. Main applications are in road planning tools and soft rock drilling tools. Part of the coarse crystallized WC for the these applications is also supplied by menstruum WC.
If you have any interest in tungsten carbide powder, please feel free to contact us by email: sales@chinatungsten.com or by telephone: +86 592 5129696.
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