Fabrication and evaluation of monolayer diamond grinding tools by hot filament chemical vapor deposition method

Abstract

Monolayer diamond grinding tools are commonly made by electroplating or brazing. However, electroplated tools involve weak grain/matrix adhesion due to a lack of chemical bonds, and brazed diamonds often suffer thermal damage resulting from the high-temperature brazing process. This paper reports a new method to fabricate monolayer diamond grinding tools by chemical vapor deposition (CVD) technique. First, diamond powders at the range of 7–180 μm are chosen as seeds of the abrasive grains. The seeds are randomly distributed on SiC substrates by spraying the suspension containing the seeds toward the substrates in a spin coater machine, or orderly positioned on the substrates by a patterned mask. Then CVD diamond growth is conducted on both the substrates and the seeds simultaneously. As-grown diamond films on the substrates are regarded as bonding layers of the grinding tools, and the original seeds with irregular and crushed morphologies can grow into blocky cube-octahedral grains with smooth surfaces, which are supposed to have enhanced mechanical strength. Raman spectra demonstrate that as-grown diamonds on both the substrates and the seeds are of high quality and low levels of graphitization. Besides, relatively low residual stresses are detected in the diamond grains, because both the bonding layers and the grains are made of diamond. Grinding tests are conducted using as-fabricated CVD diamond grinding tools and electroplated/brazed diamond grinding tools as comparisons. The results suggest that the CVD diamond grinding tools possess the best wear resistance in terms of the fracture of the diamond grains. This is attributed to the epitaxial grain structure that restrains the crack propagations. In addition, the wear of the CVD diamond grains can generate tiny pyramidal crystalline tips and sharp edges, indicating the unique shelf-sharpness during the grinding.