Plasma spraying of boron carbide using ternary gas mixtures

Materials which exhibit high specific heat and melting enthalpy combined with a low density, like boron carbide B4C, are difficult to melt by plasma spraying under standard spray conditions. Moreover, the injection of this low-density powder in the plasma jet is critical, specially when fine particles are used. The optimization of the plasma-forming gas composition may make the penetration of the particles in the gas flow easier, and improve their melting state. This paper presents an investigation of the effect of the composition of ternary gas mixtures of argon, helium acid hydrogen on B4C particles heating and acceleration. The particle injection and the resulting spray pattern in the jet were controlled by using a 1-D imaging technique. The particle velocity distribution was measured with a laser Doppler anemometer and the particle overall temperature with a high-speed pyrometer.