A suspension high velocity oxy-fuel thermal spray manufacturing route for silicon carbide – YAG composite coatings

Silicon carbide (SiC) coatings obtained through thermal spraying represent a major engineering challenge due to the high tendency of SiC to decompose during the spraying process. In order to avoid this decomposition, suspension high velocity oxy-fuel (SHVOF) thermal spray was used in combination with a novel SiC powder modified by addition of yttrium aluminium garnet (YAG) as the feedstock. The colloidal stability of the feedstock in water was optimised in order to obtain stable and well-dispersed suspensions suitable for SHVOF spraying. Dense SiC-YAG coatings with ~80 μm thickness were obtained and the coatings showed promising results in terms of porosity, microstructure, phase distribution and mechanical properties. Energy dispersive X-ray spectroscopy and X-ray diffraction showed a lack of degradation of the SiC phase in the coatings, thanks to the formation of a molten YAG phase during the spray process, which prevents SiC decomposition.