Microstructure and Properties of TiB₂ Composites Produced by Spark Plasma Sintering with the Addition of Ti₅Si₃

Titanium diboride (TiB₂) is a hard, refractory material, attractive for a number of applications, including wear-resistant machine parts and tools, but it is difficult to densify. The spark plasma sintering (SPS) method allows producing TiB₂-based composites of high density with different sintering aids, among them titanium silicides. In this paper, Ti₅Si₃ is used as a sintering aid for the sintering of TiB₂/10 wt % Ti₅Si₃ and TiB₂/20 wt % Ti₅Si₃ composites at 1600 °C and 1700 °C for 10 min. The phase composition of the initial powders and produced composites was analyzed by the X-ray diffraction method using CuK_α radiation. The microstructure was examined using scanning electron microscopy, accompanied by energy-dispersive spectroscopy (EDS). The hardness was determined using a diamond indenter of Vickers geometry loaded at 9.81 N. Friction-wear properties were tested in the dry sliding test in a ball-on-disc configuration, using WC as a counterpart material. The major phases present in the TiB₂/Ti₅Si₃ composites were TiB₂ and Ti₅Si_3. Traces of TiC were also identified. The hardness of the TiB₂/Ti₅Si₃ composites was in the range of 1860-2056 HV1 and decreased with Ti₅Si₃ content, as well as the specific wear rate W_v. The coefficient of friction for the composites was in the range of 0.5-0.54, almost the same as for TiB₂ sinters. The main mechanism of wear was abrasive.