SINTERED COMPOSITE MATERIALS BASED ON WOLFRAM-COPPER FOR MANUFACTURING ARC ELECTRICAL CONTACTS AND PROCESS FOR PREPARING THE SAME

摘要

The invention relates to sintered composite materials based on WCu to be used for manufacturing arc electrical contacts, of complex shape, such as protection rings and contact points, necessary to fit out medium and high-voltage SFgas or mineral oil insulated switchgears and to a process for preparing the same. The claimed materials comprise a mixture of pure microcrystalline powders of W, Cu and Ni with a content of 70...75% W, 0...1% Ni and for the remainder Cu, the percentage being expressed by weight, with a maximum size of W, Cu and Ni particles of 15 μ m, 63 μ m and 5 μ m, respectively, mechanically homogenized for 16 h, and an apparent density of composite powder mixtures in non-granulated state of 4.07...4.42 g/cm. The claimed process consists in preparing composite materials by vacuum spark plasma sintering the mixtures of pure microcrystalline powders of W, Cu and Ni, for 10...30 min, at the temperature of 1045...1055°C and pressing them in a graphite die with a pressing pressure of 60...70 MPa, resulting in sintered cylindrical semifinished products with a diameter ranging between 30...60 mm and a height of 3...10 mm, having a density of 14.19...14.75 g/cm, relative density of 96.5...99%, average roughness Ra = 0.10...0.14 μ m, Vickers microhardness HV 1/15 = 279...354, elastic modulus of 164...192 GPa, electric resistivity of 3.64...7.14 μ Omega.cm and thermal diffusivity at 25°C of 43...87 mm, which are mechanically machined to the desired shape and sizes for making arc electrical contacts with complex shape.