PVD Black Coating for Decorative Applications

PVD coatings have gained considerable attention as decorative coatings because they combine decorative with protective properties. Within the frame of this work, a black PVD coating based on chromium, carbon and oxygen was developed in a semi-industrial coating machine with four magnetrons and continuous substrate rotation. Based on the optical properties of CrxCyOz, the optical properties of the coating can be used in the design of the coating. EDX measurements point to an average composition of Cr0.35O0.53C0.12 for coatings with the most interesting optical properties. XPS measurements show that the chemical state of the constituting elements changes throughout the coating thickness. CrxCyOz shows a strong columnar growth which may give origin to a rough surface structure. This effect, depending on the coating thickness, allows the deposition of black coatings with a variation of strong specular reflection (“piano black”) and diffuse reflection (“matt”) for a coating thickness variation between 1 and 5 μm. The diffusive reflection increased from almost 2% to 6% for the thicker samples whereby the specular reflection decreased from about 20% to almost 0 of the samples with a thin coating and samples with a coating thickness close to 5 μm. Within the frame of this work, we also determined the functional properties of adherence and surface energy, which show that the coating can be used in demanding applications without an additional protective topcoat.