Vaporization and Poor Wettability as the Main Challenges in Fabrication of TiB2-Cu Cermets Studied by SPS

TiB2-Cu cermets with various volume fractions of copper (from 3 to 30 vol. %) were produced via liquid phase sintering at the temperature range 1100–1200 °C in vacuum using spark plasma sintering (SPS) technique. Full densification could not be achieved as the consequence of poor wettability and vaporizing Cu. The quantitative Rietveld analysis indicated that insignificant reduction in Cu content occurred only in sample with initially 3 vol. % of Cu, but then densification was negligible. The relative density improved along with increasing volume content of Cu (10–20 vol. %), but then predominant amount of Cu introduced was reduced as the effect of vaporization or swelling, which caused that pellet with intended 20 or 30 vol. % of Cu contained respectively only 6 or 17 vol. % after sintering. Moreover, Cu droplets were released from the die at the temperature of 1000–1030 °C near the Cu melting point. The effect of vaporization was successfully reduced by increased heating rate and when isothermal annealing process was skipped, however, it could not be entirely eliminated. The experimental results on Cu vaporization are confronted with parameters that are commonly considered in the production of cermets, such as oxidation, wettability, contact angle and viscosity as well as their impact on densification.