Interaction of Sn-Cu-Co powder materials with diamond in liquid-phase sintering

Abstract

The interaction of the Sn-Cu-Co powder material with diamond in liquid-phase sintering has been studied. The material contained commercially pure metal powders at the following proportion, wt. %: 21 Sn, 46 Cu, 33 Co. Metal powders and synthetic diamonds AS150 were mixed with the organic binder and applied on a steel base. Sintering was performed in vacuum at 820–1100°C. The structure of sintered materials is investigated by X-ray diffractometry, scanning electron microscopy and energy dispersive X-ray microanalysis. It has been found out that at sintering temperatures of over 900°C, the liquid phase wets and dissolves diamonds due to its containing cobalt. When the material is cooled down after sintering, the dissolved carbon crystallizes on the surface of diamonds in the form of graphite flakes, which leads to the formation of a weak layer between diamonds and the metallic matrix.

Structure Formation of Diamond-Containing Coatings during Sintering of Specially-Shaped Grinding Wheels

“…Meanwhile, Sn-Cu alloys are known to be chemically inert to diamonds and to not wet diamonds in their liquid condition [15]. Therefore, wetting of the diamonds is achieved as a result of the content of cobalt both in the liquid and in the solid phase of the binder being sintered [11,16].…”

“…To help counter this, special compositions of Sn-Cu-Co powder materials have been developed. Their sintering is accompanied by a large quantity of the liquid phase forming [10][11][12]. The liquid phase facilitates regrouping of the solid phase particles, which helps alleviate shrinkage stresses.…”