Experimental study on surface element composition and hydrophobic properties of DLC coating

Precision rubber mold is an extremely important basic process equipment in industrial production, however, there are some classic problems, such as viscose, coke accumulation and difficult demoulding, can not be effectively resolved. In order to solve this problem, in this paper, a new process of preparing high performance DLC coated precision rubber mold is proposed by using the excellent anti-sticking properties, self-cleaning properties and hydrophobic properties of DLC coating. In the experiment, steel (S35C) substrate with the same material as tire mold is used. Hydrophobic of DLC coating surface mainly depends on the surface element composition and the roughness. All the substrates are exactly processed, so as to ensure that the roughness has minimal impact on hydrophobic. Plasma enhanced chemical vapor deposition (PECVD) technology is employed to prepare fluorine doped diamond-like carbon (F-DLC) coating and hydrogenated diamond-like carbon (a-C: H) coating. Arc ion plating (AIP) technology is applied to produce Non-hydrogenated diamond-like carbon (a-C) coating. The coating is deposited on the surface of steel (S35C). Then, the roughness, the element composition and the hydrophobicity of the prepared coating are tested. Experimental results demonstrate that the water contact angle of a-C coating only 73.8 degrees, water contact angle of a-C: H coating up to 80.16 degrees, however, water contact angle of F-DLC coating could reach to 89.01 degrees, meanwhile, the surface energy can be reduced to 22.62 mN/m. To some extent, the hydrophobicity of the coating enhances with the increase of H content, and the content of weak polarization group CF2 becomes stable with the incorporation of F element. As a consequence, the surface of coating becomes smoother and the wettability of coating and water becomes poorer, therefore the performance of hydrophobic of the coating is further enhanced. © 2018 Trans Tech Publications, Switzerland.