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Titanium-molybdenum carbide nickel cermets ((Ti, Mo)C-Ni) were produced using high energy milling and reactive sintering process. Compared to conventional TiC-NiMo cermet sintering the parameters for reactive sintered cermets vary since additional processes are present such as carbide synthesis. Therefore, it is essential to acquire information about the suitable sintering regime for reactive sintered cermets. One of the key parameters is the final sintering temperature when the liquid binder Ni forms the final matrix and vacancies inside the material are removed. The influence of the final sintering temperature is analyzed by scanning electron microscopy. Mechanical properties of the material are characterized by transverse rupture strength, hardness and fracture toughness. [ABSTRACT FROM AUTHOR]

Reactive sintering is a novel process where synthesis reaction of the carbide phase is combined with solid and liquid phase sintering of the cermet during a single heating cycle. Ti-C-Ni-Mo composites were synthesized in situ from elemental powders of Ti, Ni, Mo and C by high energy milling, followed by reactive sintering. The milled powders with the grain size in nano-scale were pressed to compacts and sintered. During the sintering that was performed after pressing, the titanium carbide was formed first and then the TiC-NiMo cermet was sintered in the presence of liquid phase in one cycle. The interface between the binder phase and the carbide grains of the in situ composite has a good bonding strength because it is not contaminated with oxidation film or other detrimental surface reactions. The microstructure of such cermet is fine-grained and more homogeneous than that of cermets produced by conventional method. In the paper the phase evolution, microstructure formation and carbide grain growth during reactive sintering are explained [ABSTRACT FROM AUTHOR]

Fe-based alloys as alternative binders of cemented carbides are of increased research interest. We used ferritic chromium steel AISI430L as metallic component in cobalt and nickel free WC-FeCr cemented carbides. Composites with relatively high binder content of 30 wt% were under investigation. Our focus was on the effect of sintering temperature on the densification and phase evolution and on the influence of extra carbon. With the liquid phase formation around 1150 °C, the near full density of the composites was achieved at 1200 °C. During sintering, M 6 C η -phase and (Cr, Fe) x C y mixed carbides of different composition dependent on the carbon additions were formed. Addition of carbon to achieve over-stoichiometric carbon level proved opportunity to retard the formation of the η -phase and the (Cr, Fe) 23 C 6 phase and favored microstructural homogeneity. However, final microstructure remained heterogeneous with binder rich areas consisting of Cr- and Fe-based carbides and α -Fe. [ABSTRACT FROM AUTHOR]

Abstract: The present paper is focused on three-body abrasive wear of cermets on the base of tungsten, titanium and chromium carbides with different contents of binder phase. A series of samples of different cermets was tested using a block-on-ring test machine by the method of ASTM B611 using normal loads of 40 and 200N. Silica sand was used as the abrasive. The wear resistance of TiC–NiMo and Cr3C2–Ni cermets was compared with WC–Co based hardmetals. The volume wear of the cermets decreases with the increase of carbide content in the composites, which corresponds to an increase in the bulk hardness. The volume abrasive wear of the cermets increases approximately linearly with the sliding distance. The wear tracks of the worn compositions blocks abraded at low-load and high-load conditions were analyzed by scanning electron microscopy (SEM). Abrasive wear mechanisms are similar for different cermets, depending mainly on the material/abrasive relative hardness and loading value. [Copyright &y& Elsevier]