Abstract
This paper deals with heat treatment of synthetic cubo-octahedral diamond grains to get tight bonding by making their surface rough. In order to get rough surface, thermal etching technique in atmospheric pressure of air at 700-1 100°C is applied. The shape, surface structure and surface area are investigated. Then diamond grains are bonded with electroless plating Nickel or phenol resin and bending test is carried out to estimate the effect of rough surface on bonding strength. Results obtained are as follows. (1) Rough surfaces are obtained by thermal etching in atmospheric pressure of air. (2) Etching at 700-1 000°C, etch rate of {111} face is higher than that of {100} face, in particular, diamonds etched at 700-1 000°C have hollow {111} face. (3) Surface area of one diamond grain can be increased by etching. On the occasion of etching at 900°C for 15 min, surfaces are fully covered with clear-cut etch pits and surface area shows maximum value. (4) Surface area seems to have influence on bonding strength and when diamond grains are bonded with phenol resin or electroless-plating Nickel, bonding strength improves about 10%.
