Rapid consolidation of Al2O3-TiO2-Co nanocermets via spark plasma sintering of Co-coated ceramic particles

Abstract

In this paper, spark plasma sintering (SPS) of metal-coated ceramic particles is introduced as a rapid and low-temperature method for consolidation of Al2O3-TiO2-Co nanocermets. The microstructure of such consolidated cermets consisted of a thin and continuous Co network which embedded the Al2O3 particles. The metallic network was also reinforced by uniform distribution of Co-coated TiO2 nanoparticles. The Co coating of ceramic particles was carried out using the electroless deposition (ED) process. Structural characterization by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) indicated that the metal coating of the ceramic particles resolves the low metal-ceramic wettability limitation, and causes the preparation of highly uniform microstructure with desirable metal-ceramic interfaces. The proposed method not only reduces the time and temperature of the sintering process, but also leads to the fabrication of highly dense cermet materials without any grain growth, nanoparticles agglomeration, materials oxidation and formation of undesirable phases. Moreover, thermal and magnetic properties of the prepared samples were investigated via differential thermal analysis (DTA) and vibrating sample magnetometer (VSM) analyses, respectively. Furthermore, the effects of process parameters were modeled on the hardness and wear weight loss of the fabricated nanocermets by the means of response surface methodology (RSM). According to the optimization analysis, sintering of Al2O3-20 wt% TiO2-20 wt% Co composite powder at the temperature of 1345 °C and under 28 MPa pressure led to the fabrication of nanocermets with a minimum wear weight loss of 0.001 mg and maximum hardness of 72 RA.