Thermal residual micro-stresses and texture characterizations in NbC-Ni cemented carbides

Abstract

Cemented carbide composites develop very large micro-stresses due to the coefficient of thermal expansion mismatch between the metallic carbide and the binder phases. While micro-stresses developed in WC-Co/Ni systems have been investigated, so far, there is no information on the ones developed in NbC-Ni composites. This study aims to provide preliminary data on this matter. The thermal micro-stresses and texture developed in NbC-Ni systems were characterized by neutron diffraction. Stresses in the Ni phase were found to decrease with the increase of binder content in the composite material (from 7vol.% to 13vol.%) and ranged between approximately -2900 MPa to -1600 MPa, while stresses in the NbC phase were found to be relatively constant at approximately +240 MPa. The sintering temperature was found to have a major impact on the Ni grain number, with thousands of grains measured against just a few for samples sintered respectively at 1350ºC and 1450ºC.