Carbon Content
The carbon content of a WC powder is commonly stated as total carbon and free carbon (uncombined carbon present as graphite or amorphous carbon). The difference between these values accounts for the combined carbon (chemically bound as carbide).
The total carbon content should be theoretically 6.13 wt% carbon, which means that all carbon is chemically combined as WC. However, in practice, a small amount of uncombined carbon is always present (some hundredths of percent).
The proper total carbon depends on further processing of the powder (compact) and is dictated by the hardmetal producer, due to its processing experience (carburizing, neutral, or decarburizing conditions).
The determination method is described in ISO 3907 and ISO 3908 and should result in standard deviation of no more than +0.01 wt%.
Trace impurities.
Trace impurities play an important role in hardmetal manufacture, since they can cause numerous types of defects (porosity, inclusions, origin of local grain growth, etc.). They should be kept as low as possible in the powder, in particular when a detrimental action has already been demonstrated (as, for example, in the case of Ca, Si, Al, and S).
The impurity content of a WC powder is the result of three main factors: (1) the purity content of the starting W powder; (2) the impurity content of the carbon black or graphite, and (3)the carburization temperature (the higher the temperature, the more the trace impurities are evaporated during carburization).
Although the above characterization in regard to physical and chemical properties seems to be quite rigid and complete, in some cases unexpected and unsatisfactory results may occur during the further hardmetal production. the reason for this behavior is based on still insufficient specification, because the carbon black quality, carburization temperature, as well as type and duration of milling after carburization are not clearly defined, and can be changed by the supplier or may differ between diverse suppliers.
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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