Mechanical properties of hot-pressed ZrO2–NbC ceramic composites

In this work, the development of the composites based on yttria-stabilized Zirconia ZrO2–3%Y2O3 using different contents of niobium carbide, NbC, is proposed by uniaxial hot-pressing. Powder mixtures of ZrO2 containing 0–30 wt% of NbC were prepared, pre-compacted and submitted at uniaxial hot-pressing, at 1600 °C or 1650 °C, under pressure of 20 or 40 MPa, for 30 or 60 min. Crystalline phases were identified by X-ray diffractometry. Furthermore, relative density was obtained using Archimedes method and microstructure was observed by scanning electron microscopy. Fully dense samples were obtained using different sintering conditions. Samples with hardness between 1300 and 1500 HV were obtained as function of the NbC addition in the ZrO2 matrix. The results of fracture toughness indicate variations between 5.4 MPa m1/2 and 6.3 MPa m1/2. A reduction in fracture toughness is observed as a function of NbC increasing. The increasing of sintering temperature (1650 °C) and isothermal holding time (60 min) in the samples with 30% NbC, inhibit this effect, promoting the obtaining of hard and toughened ceramic composites.