Properties of ultrafine Cu-64WC composite obtaining by vacuum hot pressing

Abstract

Ultrafine mixture of tungsten carbide and copper powders with volume fraction of tungsten carbide 50% (64% (wt.) was prepared by the intensive grinding in a ball drum with hard-alloy balls. After grinding one part of mixture was kept on air, and second processed hydrogen at 400 ^оC during 2 hours. The densification in a vacuum to one and to other part of mixture at different temperatures and at the use of two methods – ordinary sintering and hot-pressed under pressure 1000–-1200 MPa was investigated. It is find out that heating of raw preforms from ultrafine mixture in a vacuum allows to get high-quality specimens even from more oxidized mixture and level the role of mixture hydrogen rough-down, decreasing the initial oxygen content . The hot pressing with the high level of pressure provides the obtaining of high-density, 92%, at the temperature of 750 oС, while the liquid sintering at 1150 ^оС during 20 min results in the relative density 88%. However, high-dense specimens obtaining at a low temperature possess lowered conductivity and mechanical properties, presumably, from low quality of boundaries. The high level of mechanical properties is achieved at the hot pressing densification in area of temperature of 1050 ^оС. At the indicated densification temperature this composite has a ultrafine structure (size of WС particles 0,3–0,5 мкм) and followings mechanical properties: transverse rupture strength –1800 ± 80 MPa, compression strength – 1970 ± 260 МPа, HV10 hardness – 3840 ± 290 MPa.