Unusual material removal characteristics of the novel graphite/diamond composite in mechanical polishing

Abstract

Novel graphite/diamond composite (Gradia) is ultrahard, tough and semiconductive. Surface finishing of Gradia is difficult because of the disparity in mechanical properties between diamond and graphite components. In this work, material removal characteristics of Gradia in mechanical polishing were studied with experiments and molecular dynamic simulations. First, the Gradia surface was well-finished. Then, microstructural investigation showed the main mechanism of phase transformation was amorphization during polishing. The graphite and diamond phases of Gradia underwent interconversion under the mechanical action. In addition, initial and diamond-transformed graphitic phases experienced distortion, twist and reconstruction, producing graphite film. Finally, a Gradia tool was created and demonstrated a lower wear rate than single-crystal diamond tool, suggesting an unusual self-lubricating characteristic with abrasion-induced generation of graphite.