Abstract
In order to provide a strong bonding between diamonds and matrix, a typical matrix alloy contains copper and cobalt as base metals, and tin, chromium and titanium as additives. Copper has a high thermal conductivity to dissipate heat during grinding together with a low degree of lattice disregistry to diamond to provide bonding strength. Cobalt has rather high values of both modulus of elasticity and elastic limit, and a low coefficient of thermal expansion to be compatible to some extent with the high elastic properties and the low thermal expansion of diamonds during grinding. Those properties make the matrix hold diamond grit tightly. Tin reacts with diamonds to form rough surfaces leading to an increased mechanical bonding strength, while chromium and titanium react with diamonds to make carbide layers on the grits leading to a good bonding strength provided by a good wetting. In the presence of a liquid copper alloy, iron or cobalt forms a solid solution layer containing copper as a main solute on graphite surface. The formation of the layer is driven by a difference of chemical potential in the system. A similar layer formation is possible on diamond surface. The layer will provide tight holding of grits by matrix.
