The Metallization of Diamond Grits
Diamond grits in tools are typically held in a sintered matrix of metal powder (e.g. Co). The bonding between diamond and the matrix is essentially mechanical. As a result, most diamond grits are easily knocked out from the tool during cutting. The diamond industry has designed various metal coatings (e.g. Ti, Cr, Si) to improve the adherence of diamond grits in the matrix, but the improvements have been modest (e.g. up to 50% increase of tool life). A revolutionary “Active Braze Coated Diamond” (ABCD) is now being developed. The coating of ABCD is much thicker (e.g. 20 microns) than conventional ones (about 1 micron). The molten braze is wetted and reacted with diamond to form strong chemical bond at the interface so that the diamond does not become knocked out of tools. ABCD is coated with a nickel alloy that can form metallurgical diffusion bonds readily with the metal matrix of the tool. In essence, ABCD turns diamond into a metal grain so that the diamond tools can be made by conventional powder metallurgical process without being concerned about the poor bonding between matrix metal powder and the diamond as before.
Duk Yong Yoon, Suk-Joong L. Kang, Kwang Yong Eun and Yong-Seog Kim
J. C. Sung et al., "The Metallization of Diamond Grits", Materials Science Forum, Vols. 534-536, pp. 1137-1140, 2007