Functional-gradient WC-TiC cemented carbides with alternative binders (Ni and Fe)

Abstract

In this work we investigate the development of functionally graded cemented carbides, featuring macro gradients on the millimeter scale, where Fe, or Ni is the binder phase. Two composites, WC-Ni and WC-Fe with 20 % binder by volume were produced by addition of TiC on the surface of the samples before sintering at 1475 °C for 1 h. The sintered samples were analyzed using electron microscopy and microanalysis.

For the Ni-binder sample, the results show a clear WC grain size gradient, with the smallest average grain size close to the TiC layer. This sample also exhibits compositional gradients, where Ni increases while Ti and C decrease from the added TiC layer and outward. The same effect of TiC addition on WC grain growth is observed in the Fe-binder sample, however, the effect is much smaller.

The addition of Ti is known to influence the morphology of WC grains in Co-binder systems, and this effect is observed here in both Ni- and Fe-binder samples. WC growth ledges areobserved on the WC facets near the applied TiC layer where Ti levels in the binder are high. This suggests that the WC grain growth inhibition mechanism imposed by Ti is similar in these alternative binders as what has previously been reported for conventional Co-binders.