ZrB2 based novel composite with NiAl as reinforcement phase

ZrB2 based novel composites have been prepared using NiAl as reinforcement phase. Three samples of compositions (a) ZrB2 + 5%NiAl (a) ZrB2 + 10%NiAl (a) ZrB2 + 20%NiAl were prepared by hot pressing at 1700 °C. All the three samples were densified to a density of > 94% of its theoretical value. Addition of NiAl resulted in liquid phase sintering and assisted in densification. The composite was characterized by mechanical property measurement and microstructure analysis. Flexural strength of the composite was found to be in the range of 421 to 438 MPa. Hardness of composite was found to decrease with addition of NiAl. Indentation fracture toughness was found to increase with increasing NiAl content. Microstructural characterization revealed the uniform distribution of NiAl phase in ZrB2 matrix. Grain coarsening was observed in composite with higher NiAl content. Fracture surface analysis revealed that the mode of fracture is transgranular. Microstructure analysis of crack propagation revealed the presence of crack bridging and crack arrest near NiAl phase, which resulted in higher fracture toughness of 6.8 MPa·m1/2. Isothermal oxidation study at 1400 °C revealed that the developed composite has good oxidation resistance.