The scope for pressing and sintering diamond-bearing components in shock waves

Abstract

The most highly stressed materials of that type are diamond-bearing composites having matrices composed of tungsten-cobalt hard alloys (slavutich and tvesal) [2, 3]. Those composites are made by hot pressing and have extremely high wear resistance, but they disintegrate rapidly because of their low strength under conditions of dynamic or cyclic loading. Their physicomechanical properties do not meet the rapidly tightening industrial requirements. The main factor responsible for weakening is the damage to the diamond grains, which is due to the cracking in them when the structure is formed [4, 5]. The physical significance can be evaluated from the proportion of grains containing cracks in unit volume. Grain-size analyses on recovered diamond grains have shown that the damage is functionally related to the mode of sintering, the diamond grade, the grain size, and the diamond concentration [4, 6]. Diamonds are damaged during hot pressing not only because of the solvent metal inclusions they contain, the technological defects, and the state of strain in the mold, but also because the method is used at P and T such that the diamond does not pass from the brittle state to the plastic one. High-pressure equipment has substantially reduced the damage to the diamond grains [5] and thus confirms that P and T influence the damage. A second factor that reduces the strength is the stress concentration near the diamond grains. However, the strength of tvesal as a function of diamond grain size below which stress concentration does not occur and the composite can be considered as a macroscopically homogeneous medium damaged by the joint action of the uniformly distributed residual temperature-dependent and mechanical stresses [6, 7].