Adsorption and diffusion behaviors of Ni-based filler elements on diamond surface

Ni-based filler alloys are widely used in brazed diamond tools due to its high hardness, good wear resistance and favorable wettability for diamond. However, the fundamental understanding of microscopic interactions between Ni-based filler elements and diamond is still lacking. Herein, the adsorption and diffusion behaviors of Ni, Cr, B and Si elements contained in Ni-based filler alloy on diamond surface are systematically investigated through first-principles calculations. The results indicate that Ni and Cr atoms prefer to adsorb at hollow (H) site on diamond (111) surface, while B and Si atoms prefer top(2) (T-2) site. Among them, Cr atom presents the stronger adsorption and diffusion abilities on diamond (111) surface, which provides internal conditions for Cr to migrate towards interface between diamond and filler alloy, resulting in enhanced interfacial bonding. The co-adsorption of Cr, or B, or Si with Ni is conductive to the enhancement of adsorption ability for matrix element Ni on diamond surface. In addition, the diffusions of Ni, Cr, B and Si atoms into diamond (111) slab are shown to be much more difficult than those on diamond (111) surface, which may be originated from the dense surface structure of diamond and the stronger bonding interactions between the 1st C bilayer and adsorption atoms. Finally, the differences in adsorption abilities of Ni-based filler elements on diamond (111) surface are analyzed from aspect of electronic structures. The results could provide an important theoretical guidance for optimizing and designing filler alloy systems for brazed diamond tools. (C) 2020 Elsevier B.V. All rights reserved.