Spark plasma sintering of self-propagating high-temperature synthesized TiC0.7/TiB2 powders and detailed characterization of dense product

In this work, the fabrication of bulk TiC0.7/TiB2 nanostructured composites through metastable transformation processing is investigated by taking advantages of two non-conventional powder metallurgy methods. First, the highly metastable TiC0.7/TiB2 agglomerated powders are synthesized by the so-called self-propagating high-temperature synthesis (SHS), followed by rapid quenching. Then, the spark plasma sintering (SPS) method is adopted to consolidate the SHSed powders. A bulk ceramic composite with nanocrystalline microstructure characterized by a high-relative density is then obtained. Dwell temperature of 1400 degrees C, heating time of 3 min, and total processing time equal to 5 min, while applying a mechanical pressure of 20 MPa, are found to be the optimal SPS experimental conditions in order to obtain near-fully densified samples. The obtained TiC0.7/TiB2 samples exhibit hardness HV5 as high as 24 GPa, modulus of elasticity of about 400 GPa, fracture toughness of about 5.6 MPa m(1/2), and a compressive strength of about 2.9 GPa. A very low-wear rate (W-nu = 3.8 x 10(-6) mm(3)/(N m)) and a good thermal shock resistance (Delta T-c = 250 degrees C) are also displayed. In addition, a high-abrasive wear factor (AWF) equal to 1.84 is evaluated on the basis of the achieved mechanical properties. These results make the obtained TiC0.7/TiB2 composite suitable for wear resistant parts as well as cutting tool materials. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.