Microstructure and Properties Characterization of Silicon Coatings Prepared by Vacuum Plasma Spraying Technology

Silicon coatings were fabricated by vacuum plasma spraying technology. The morphology, composition, and microstructure of the coatings were investigated by FESEM, XRD, WDX, and TEM. The physical, mechanical, and thermal properties of the coatings were characterized. The results showed that vacuum plasma sprayed silicon coatings were compact and consisted of well-molten silicon splats. The oxidation introduced by the spraying process was limited. Small ball-like particles of size less than 1 μm existed both on the surface and inside of the coatings. The silicon coatings were made up of silicon grains with irregular shapes and different sizes of 0.5-1 μm. The longitudinal microstructure of silicon coatings exhibited typical two-layer microstructure of equi-axed nanometer grains and overlying columnar grains. The open porosity, density, and surface roughness of silicon coatings were 3.2%, 2.24 g/cm³, and 3.47 μm, respectively. And the microhardness and bonding strength of silicon coating, respectively, were 7.0 GPa and 20.6 MPa.