Pressure sintering kinetics of tungsten and titanium carbides

The rheological model of deformable, irreversibly compressible, porous body based on mechanics of continua, and creep theory of crystalline materials, is used to describe quantitatively the compaction of the tungsten and titanium carbides powders under pressure sintering in isothermal conditions. Densification of the porous body occurs under action of Laplace's pressure, generated by surface tension, and applied pressure. The estimated mean value of Laplace's pressure was determined to be 5.8 MPa for tungsten carbide and 7.2 MPa for titanium carbide. The densification kinetics of tungsten carbide in the sintering range of 2100–2500 °C and titanium carbides in the sintering range of 2100–2700 °C are controlled by the mechanism of nonlinear steady-state creep, which occurs at a rate proportional to the fourth power of stress in carbide matrix forming porous material. The estimated values of activation energy for the powder particle power-law creep rate are 591 kJ/mol for tungsten carbide and 573 kJ/mol for titanium carbide during the pressure sintering in initial and intermediate stages. These values indicate that a climb dislocation mechanism controlled the creep, and the values are consistent with the activation energies of bulk diffusion in metal sublattice of carbides. A diffusional creep controls the pressure sintering kinetics in a later stage.

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• Rheological model of deformable irreversibly compressible porous body
• Pressure sintering kinetics of tungsten and titanium carbides powders
• Estimated activation energy for the powder particles power-law creep
• Different mechanisms controlled pressure sintering kinetics