The Effects of Sinter-Hip Processing on the Machining Performance of Cemented Carbides Based on NBC-NI Systems as Alternative Cutting Tools

Abstract

This work aims to investigate the technical feasibility of using sintered carbides based on NbC-Ni substitute of the WC-Co class, adding the Sinter-Hip step in the sintering process, with 20 bar pressure nitrogen gas. The samples were produced investigating two process variables: sintering cycles and chemical composition. The samples were qualified in terms of Vickers hardness, toughness and density by Archimedes. The machining experiments were carried out on quenched and tempered AISI 4340 steel material. Flank wear progression was defined as the control parameter, analyzing wear via CCD camera, stereoscopic magnifying glass and SEM/EDS. The best result obtained the binding phase content 10%w, when compared to a commercial WC-Co insert. It showed superior performance at 88% of the average life of the cutting edge. However, the dispersion of this lifetime was higher than the WC-Co reference tool, 15%. The samples of NbC-10%p Ni showed a higher level of porosity than WC-Co. For better densification, new samples with the same composition were produced by adding the Sinter-HIP step. New tests were carried out and the results showed that the adjustment of the sintering process was fundamental. Densification and microstructure alteration reduced the dispersion of the average lifetime of this new NbC-Ni class.