Modeling the infiltration kinetics of molten aluminum into porous titanium carbide

Capillary-induced melt infiltration is an attractive method of fabricating metal/ceramic composites, as it offers the advantage of producing material with a high ceramic content and near-net-shape fabrication, without the use of an external force. In this work, the kinetics of infiltration of molten Al in TiC preforms, having a pore size of approximately 1 μm and porosity ranging from 20 to 40 pct, were investigated. The rate of infiltration was continuously monitored using a Thermo-Gravimetric analyzer (TGA), which measured the weight change of the preform as the metal intruded the sample. Infiltration profiles where generated over a temperature range of 860 °C to 1085 °C. At lower temperatures, an incubation period was evident in the profiles. The average activation energy for the different preforms was 90 kJ/mol, indicating that some form of mass-transfer mechanism was involved in driving the process. Furthermore, sessile drop tests showed an unstable wetting angle over a long period of time. Such wetting kinetics were responsible for the incubation period during the infiltration. The infiltration rate was also seen to be slower as the preform density increased. This was due to the tortuous nature of the channels and was characterized using curves obtained for liquids infiltrating the same preforms at room temperature. Both the tortuosity and the unstable contact angle have to be considered when modeling the infiltration kinetics of such a system. The existing model was therefore modified by incorporating terms to describe the process more accurately. A good correlation with the experimental data was seen to exist. Formerly Graduate Student, Department of Metallurgical Engineering, McGill University     

Thermodiffusional treatment of chromium carbide hard metals

Conclusions It has been established that the cementing phases of P/M chromium carbide and titanium carbide hard metals can be superficially hardened by thermodiffusional impregnation with phosphorus. Treatment of these alloys for 3–7 h at 1000°C in an alumina filler containing 30–70% of nickel phosphide and subsequent 1-h annealing at 400°C increase the surface hardness of their binder phases by 1.5–3 GPa. Thermodiffusional treatment doubles the wear resistance of KKhN35 alloy operating under hydroabrasive wear conditions.Translated from Poroshkovaya Metallurgiya, No. 12(240), pp. 69–73, December, 1982.     

Structural changes in the surface of titanium carbide and tungsten carbide hard alloys with nickel binder upon exposure to laser radiation

Pulsed laser action on cemented titanium carbide with nickel—chromium binder yields deep changes in its structure; and in the case of cemented tungsten carbide with nickel binder, the structural change is accompanied by phase transformations in the heat-affected zone. As a result of these changes, layers with thickness 30–60 µm and 30–60% greater hardness are formed. When the energy density of the laser radiation is higher than 200 J/cm², thermal failure of cemented carbide surfaces occurs (observed as crack formation).     

Physicomechanical and fatigue properties of titanium carbide base sintered carbides

Conclusions In strength properties KTS-1N alloy is close to the standard tungsten carbide base sintered carbides while in hardness it exceeds them. This material possesses high high-temperature strength, scale resistance, and cyclic resistance. As the result of the action on the material of periodically acting compressive loads of up to 4 GPa fracture occurs primarily in the plastic binder.Translated from Poroshkovaya Metallurgiya, No. 3(267), pp. 74–78, March, 1985.     

Production of gradient structures in sintered TiC−(Ni,Mo) hard alloys on interaction with molten metals

Kinetic trends have been identified for mass transport of molten metals into sintered TiC?(Ni, Mo) hard alloys. Conditions have been identified for the mass transfer of the liquid by the migration and diffusion-migration mechanisms. Details are given of the formation of gradient structure in the TiC?(Ni, Mo) hard alloys on interaction with molten metals, where it is found that there are effects from the physicomechanical properties of the materials.