Novel approach to deposit thermally-sensitive materials using hybrid plasma spraying

Hybrid plasma spraying has been proved to provide novel coating microstructures as a result of the simultaneous injection of a dry coarse powder and a liquid feedstock into the plasma jet. Such microstructure contains both large splats originating from the conventional dry powder and finely dispersed miniature splats deposited from the liquid. This approach enables preparation of coatings from virtually all materials which are conventionally processed using plasma spraying. However, incorporation of materials susceptible to decomposition at high temperatures is still challenging even using this concept due to the high thermal energy provided to all feedstocks to be deposited. Hereby, we propose an innovative work-around approach of incorporation of thermally-sensitive materials into a coating sprayed using a high-enthalpy plasma torch. The influence of the deposition conditions on retention of the added materials in the coatings was evaluated using scanning electron microscopy and x-ray diffraction.