Coatings on diamond grits enable the tool manufacturer to choose an inexpensive bond material with iron, which otherwise would shorten the diamond life time [KOMP05]. In addition, elevated tool manufacturing temperatures can be applied [KOMP05].
2.7.1.3 Grit Alignment During Tool Manufacturing
Grits for coated tools are coated to enhance their electrostatic properties. A grinding belt passes through an electrostatic field so that each grit is polarized and aligns with the field. [UAMA09]
2.7.1.4 Grit and Bond Protection During Tool Use—Heat Transfer
In resin bonds, coatings work as a heat sink absorbing temperature peaks during grit-workpiece contact and prevent the resin bond from burning up [DYER79]. In particular, diamond with its high thermal conductivity transfers the grinding heat fast to the resin mass, which might burn. Grit coatings disperse the heat first into the coating and thermal stresses of the bonding can be reduced [METZ86, p. 42]. The grinding processes can be more efficient due to the coating’s ability to act as heat sink [HERB81]. Bfittner [BUTT68, p. 82] described one example for the heat insulating effect of nickel-phosphor coating on diamond grits in resin bond.
Metal coatings transport the process heat from the grit into the wheel bonding. The life time of heat sensitive diamond grits increases. Copper coating is a more conductive metal layer than nickel alloy for specialized bonds, so that there are some applications where copper coated diamond in resin bonds works well for grinding tungsten carbide [NOTT76].