Studies of graded cemented carbides components

Graded structures obtained by coupling different WC grades, also containing cubic carbides type (Ta, Nb)C with Co as binder, were produced by vacuum sintering. Different batches of cylindrical samples were compacted by coupling two different grades and were sintered at 1450°C under vacuum. The hardness properties as well as the shrinkage due to sintering process are function of the employed grades and show gradual change between the single values of each of the coupled grades. The residual porosity was always lower than type A02, the observed microstructure shows very good link between the coupled grades, with the presence of a diffusion zone and without any influence of gravity on structure. The results show that it is possible to produce multilayer graded tools with a tough core, constituted by cheap carbide grades with high binder contents, covered by a very hard surface layer, achieving high economical and technical competitiveness for the production of tools for applications in high abrasive as well as in shock loaded environments.