Rhenium coating prepared on carbon substrate by chemical vapor deposition

Rhenium coating was prepared on the isotropic graphite and C/C composite by chemical vapor deposition. The phase composition and microstructure of the coating were studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The results show that the rhenium coating on the isotropic graphite was compact and crack-free with a preferential growth orientation of 〈0 0 2〉 while two kinds of cracks were found in the coating on the C/C composite. The formation of the two cracks in the coating on the C/C composite was mainly attributed to the residual stress resulting from the mismatch in the thermal coefficient of expansion and the anisotropy of the C/C composite. Furthermore, the bond strength between the rhenium coating and the substrate was tested by the coating-pull-off method. The graphite substrate fractures with the tensile strength about 4.5 MPa for the coating on the graphite, while the rupture is at the interface of coating-adhesive for the coating on the C/C substrate with the tensile strength of 15 MPa.