Fracture toughness determination and microstructure investigation of a B₄C-NanoTiB₂ composite with various volume percent of Fe and Ni additives

Boron carbide (B₄C) has wide application in manufacturing of abrasives and cutting tools, due to its unique features such as high hardness, good wear resistance, low specific weight and chemical stability. An additive reinforcing phase and sintering aids are used to improve its sinterability. In the present paper, a B₄C composite with 10vol.% of titanium diboride nanoparticles (TiB₂) and a 0, 1.5 and 2.5vol.% iron or nickel metallic additive, respectively, was mixed in an isopropanol environment containing tungsten carbide pellets. After drying, the obtained mixture was formed by cold pressing. The obtained parts were sintered at 2400°C. The effect of adding metallic sintering aids on the mechanical properties and microstructure of the composite was investigated and fracture toughness values were evaluated by indentation test method. Addition of Fe and Ni improved values for density, hardness, Young's modulus and fracture toughness, with Ni addition increasing the values considerably. Scanning electron microscope (SEM) images of the microstructure of the specimens showed the arrangement posture of the additives and confirmed the results obtained. Additionally, the FeB and Ni₃B blades formation were observed from the images.