DEVELOPMENT OF IMPROVED CUTTING TOOL MATERIALS

Cemented-carbide tool materials with refractory metal binders have been developed that exhibit exceptional cutting capabilities under conditions of high feeds and speeds on Rc 53, 4340 steel. Those experimental materials with the greatest potential contain a Ni-Cb or Co-Mo refractory matrix in combination with WC.TiC solid solutions plus additions of TaC. The wetting propensities of Cb and Mo were enhanced by the alloying additions enabling the densification of ball-milled powders by hot pressing. Liquid phase sintering was achieved at temperatures extending to 2000 C and pressing pressures ranging to 5000 psi. These materials are characterized by transverse rupture strengths exceeding 125,000 psi and hardness above RA93. Wettability and compatibility studies of various refractory alloys, Co-Ta, V-Ta, Co-W, Cr-Cb and others, in combination with TiC, TaC, ZrC, HfC, WC and WC.TiC 70/30 w/o solid solutions were conducted. Dense heterogeneous materials were evaluated by microstructure, mechanical properties, X-ray diffraction analyses and single-point turning tests. An impartial testing laboratory, Metcut Research Associates, performed extensive machinability tests on all potential materials during which experimental tools were compared to commercially available tools. Comparative tool-life curves graphically portraying the excellent performance of the experimental materials were provided by the Metcut laboratory. (Author)