An unexpected effect of selective deposition of metallic particles on the {111} facets during mechanical treatment of diamond crystals in a planetary mill

Abstract

The understanding of the processes occurring during friction at diamond/metal interfaces is of great importance for improving the performance of abrasive materials and developing the efficient methods of coating deposition on the diamond surface. The present work reports the morphological, structural and compositional changes of diamond microcrystals treated in a high-energy planetary mill. The starting diamond crystals were of cuboctahedron and truncated octahedron shapes and had sizes of 50, 100, 200 and 500 μm. The treatment was conducted in two modes, namely, with and without milling media. The milling vials were made of stainless steel. When milled with steel balls as the milling media, the diamonds were ground and experienced significant shape changes. In addition, iron was found as a separate phase in the product of milling. An unexpected effect of selective deposition of fine particles of a Fe-based alloy on the {111} facets of diamond crystals during their treatment without milling media was observed. After treatment, the shape of the crystals was well preserved. The selective deposition was found to be independent of the crystal size. Possible explanations of the observed effect were proposed.