RESEARCH OF FEATURES OF CONSOLIDATION OF ANTI-FRICTION MATERIALS BASED ON POWDER MIXTURE Cu–Pb–C

Abstract

The article represents the results of research of various methods of obtainingantifriction material "copper-lead-graphite" by methods of powder metallurgy. With the help of hotvacuum electroconsolidation of powders, which is effective for refractory materials, the conditionsfor separate cold pressing are determined, namely, product formation at 500 MPa and sintering at900 °C, which is more productive for metal powders.The initial formation of the samples was carried out in a collapsible steel mold on a hydraulicpress with a force of up to 200 tons from a mixture of powders of copper, lead and graphite, whichhad dimensions of 60–200 μm. Sintering was performed in a vacuum oven at temperatures of 700–900 °C for 20–30 minutes. To obtain a density of more than 5.6 g / cm3, it is necessary to significantlyincrease the pressure during the formation of powders. During the formation of the dry mixture,compression transverse cracks appear.Liquefied kerosene was selected from the list of studied organic liquids, which allowed to obtainhigh-quality products without cracks with a density of 5.6–5.9 g/cm3 at a load force of about 500 MPa. Sintering was performed in an inert nitrogen environment, which reduced lead losses to2–5 % at temperatures above 700 °С. Nitrogen was first supplied to the vacuum chamber to apressure of 1 atmosphere, and after increasing the temperature in the chamber, the nitrogen pressurerose to 1.2 atm.The hardness of the obtained samples was 42–46 HB according to Brinell (135–150 MPa).Machining of samples with different cutting tools was performed at different speeds and showed goodmachinability. Processed parts during storage have not changed their size. With the help of thedeveloped technology it is possible to produce composite materials with a density of 4.4–6.2 g/cm3and a Brinell hardness of 30–48 HB (99.9–159 MPa).