Although many similarities between tantalum and niobium, we cannot replace tantalum by niobium to an unlimited extent. Here we are talking about one aspect of the problem, mentioned before, because (Ta, Nb) C in Co wettability is poor, they rely on the job and WC solid solution, therefore, tantalum and niobium content can not be increased indefinitely in cemented carbide powder.
Ta: atomic weight of 180.95, Nb atomic weight:92.91, tantalum in number of atoms nearly twice more than of niobium, while they Ti, W substitutional solid solution is a solid solution, the solid solution is greatly influenced by the number of atoms. Therefore, the original alloy powder tantalum content can not be replaced with unlimited niobium. So how much will be appropriate?, I think TaC: NbC 8: 2 the most appropriate (specific proportion will depend on cement carbide performance).
Because the cemented carbide with such a proportion show the same performance of the original full-containing tantalum carbide. In addition, there is not much difference in carbide density, shrinkage factor compacts, sintering system. If the ratio is smaller, there is no longer the economic value of this transformation.
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