Interfaces are investigated at different scales in two alloys in order to get information on the processes occurring during sintering. In WC-Co alloys, the effect of composition including carbon potential and grain growth inhibitor addition on WC grain morphology is studied. The C/W ratio strongly influences the interface energy anisotropy and the limiting step for grain growth. The addition of Cr produces effects similar to W excess. Concerning VC, the hindrance of WC grain growth is depicted from the accurate distribution of V in the alloys. Fe doping element in W-Cu alloys increases the densification rate. Its location in W/W grain boundaries allows a mechanism based on enhanced grain boundary diffusivity to be proposed.