Adhesion of nanostructured diamond film on a copper-beryllium alloy

Microwave plasma chemical vapor deposition (CVD) was used to coat nanostructured diamond onto a copper-beryllium alloy (similar to 1.7 wt% Be) commonly used as a nonmagnetic gasket material in diamond anvil cell devices. The coating is expected to be useful in preventing plastic flow of Cu-Be gaskets in diamond anvil cell devices, thus allowing for increased sample volume at high pressures and leading to improved sensitivity of magnetic measurements. The coatings were characterized by Raman spectroscopy, glancing-angle x-ray diffraction, microscopy (optical, scanning electron, and atomic force), Rockwell indentation, and nanoindentation. CVD diamond deposition on pure copper substrates has historically resulted in poor coating adhesion caused by the very large thermal expansion mismatch between the substrate and coating as well as the inability of copper to form a carbide phase at the interface. While an interfacial graphite layer formed on the pure copper substrates and resulted in complete film delamination, well-adhered 12.5 mu m thick nanostructured diamond coatings were produced on the copper-beryllium (Cu-Be) alloy. The nanostructured diamond coatings on Cu-Be exhibit hardness of up to 84 GPa and can withstand strains from Rockwell indentation loads up to 150 kg without delamination.