Synthesis and characterization of nano-polycrystal diamonds on refractory high entropy alloys by chemical vapour deposition

Growing diamond has been a long-standing challenge. It is found the diamond grows on refractory metals (such as Zr, Hf, Ti) hardly to form a continuous film with a high nucleation density because of diffusion of carbon. In this study, we reported an approach to grow diamond on high entropy alloys (HEAs) of TiZrHfTaMo, TiZrHfNbMo, TiHfNbTaMo as substrates by chemical vapour deposition. Diamond films with a nucleation density as much as 108 ∼ 1010 site/cm2 grow on the mixed-carbides XC (X = Hf, Zr and Ta etc.) layer, which is 2 ∼ 3 orders of constituent metals. The orientation relationship is identified as diamond[0 1 1] // XC[0 0 1] with XC mixed-carbides by high resolution transmission electron microscope. The continuous diamond films can be obtained within 30 min. The high nucleation density and rapid growth on HEAs refer to solubility of carbon and relative nucleation energy barrier. Moreover, the corrosion of current specimens in 3.5 wt% NaCl solution have been improved (e.g., corrosion potential value is as much as −0.02 V/SCE) because of the continuous diamond film. Current result facilitates promising industrial applications of HEAs and diamonds by combining the advantages of them.