SiC particulate reinforced Al–12Si alloy composite coatings produced by the pulsed gas dynamic spray process: Microstructure and properties

The work presented in this paper examine the possibility of using the pulsed gas dynamic spraying (PGDS) process as a new production technique of Al–12Si alloy coatings and (Al–12Si + SiCp) composite coatings using feedstock powder containing 20, 40, and 60 (vol.%) reinforcement particles. In this study the effect of the processing conditions, in particular the gas preheating temperature and pressure and the feedstock particle preheating temperature on the coatings microstructure is investigated in order to optimize the spray parameters. Different analysis techniques (OM, SEM, XRD, and microhardness) as well as adhesion strength testing are used to characterize the coatings produced. Detailed comparisons of powders and coatings microstructure, phase composition, microhardness and adhesion strength are presented and discussed. Moreover similarities and differences with coatings prepared by other techniques, namely thermal spray (TS) and cold gas dynamic spray (CGDS), are presented and discussed. It was found that PGDS allows producing dense Al–12Si alloy coatings and (Al–12Si + SiCp) composite coatings with good adhesion properties while retaining a large fraction of the SiCp present in the feedstock powder. Using the shear test standard (EN 15340), analysis showed that the adhesion strength of the PGDS coatings was slightly superior to the CGDS coatings, but still lower than TS coatings. It was also demonstrated that the adhesion strength decreases as the SiC content in the coating increases.