Different surface states of carbon/carbon substrate on the sprayed calcium phosphate coating shear strength

In order to enhance the shear strength of supersonic atmospheric plasma sprayed (SAPS) calcium phosphate (Ca-P) coating‑carbon/carbon (C/C) substrate, various surface states of the C/C substrates are investigated which is the other method based on the microwave-hydrothermal (MH) post-processed C/C substrate to increase the bonding strength between the substrate and coating. In this case, surface states including density and roughness of C/C substrates were discussed. Meanwhile, surface morphologies of the C/C substrate as well as section-across images of coatings are observed by scanning electron microscopy (SEM). X-ray diffraction is for the analysis of crystalline phases in a coating. 3D confocal laser microscope is used to detect the surface roughness of the C/C substrate. Besides, shear bonding strength of the coating is utilized to detect the shear strength. Basic reference of the C/C substrate to a density of 1.40 g/cm ³ , obtained results reveal that, after changing the density of the C/C substrate to 1.70 g/cm ³ , the shear strength between sprayed Ca-P coating and substrate decreases by 22.93%. Furthermore, when the surface roughness of the C/C substrate is 16.56 ± 0.51 μm and 13.22 ± 0.65 μm, the shear strength between the substrate and coating increases by around 68.79% and 23.31%, respectively.