The aim of this work is to reinforce particulate porous SiC samples by the in situ synthesis of -Si3N4 nanofibers within the porous samples by the chemical vapor infiltration method without catalytic metallic precursors. The experiment considered the variation of the reaction time (1, 2, 3, and 4h) and the N-2 flow rate (3, 5, and 9cm(3)/min); while the inner pressure (10 mbar), the thermal decomposition of the solid precursor Na2SiF6 (400 degrees C), and the temperature of the SiC sample (1300 degrees C) remained constant. The mechanical properties of the composites revealed a non-linear behavior due to the arrangement of the particles during the loading process and to the plastic properties of the -Si3N4 nanofibers. The stress and strain energy density magnitudes for different times had a rising behavior up to 3h (sigma=15.65MPa and u=2.41MJ/m(3)) due to the increasing diameter (100 to 200nm) and quantity of -Si3N4 nanofibers; while, at 4h were significantly decreased (sigma=8.83MPa and u=1.44MJ/m(3)) based on the reduction of the -Si3N4 nanofiber diameter (30 to 100nm) and to the presence of a new phase (Si2N2O).