Nanocomposites and nanomaterials

Formation of tribotechnical composite layer on the base of Cu-Al-Fe system reinforced with nanosized particles by liquid phase metallization method
Shcheretskyi V.O., Zatulovskyi A.S., Shcheretskyi O.O.
Composite materials Department, Physico-technological Institute of metals and alloys of the NAS of Ukraine. bul. Vernadskogo, 34/1, Kyiv-3142, Ukraine. 
E-mail: shcheretskyi@nas.gov.ua

Proceeding from the materials` requirements for dry-friction bearings, a functional layered composite material (LCM) consisting of a steel base and a composite copper-based tribotechnical layer is proposed. As a steel base, middle-carbon steels are used, composite matrix is CuAl8Fe3.
The Cu-Al-Fe system bronzes have excellent mechanical, anticorrosive and antifriction properties. The technological solution for obtaining LCM by metallization consists of introducing aluminum into a copper melt directly at the stage of liquid metallization in the form of granules with nanoscale reinforcing particles fixed on the surface, the iron is diffusing directly from solid steel lining - the rigid basis of the LCM. The equilibrium content of iron in copper at the temperature of 1150 ° C is 3,9 mas. % corresponds to the content in CuAl8Fe3 bronze. The elements providing the mechanism of diffusion metallization in the contact area are copper and aluminum in the form of powders (160-200 microns), increasing of resistance to mechanical wear is provided by nanoscale carbides, nitrides and oxides, obtained by the electric-spark dispergation (ESD) and be deposited on surface of metal powders. The final phase composition, structure, properties, and therefore the operating characteristics of the produced LCM depends on and determined by the technological parameters of the metallization, matrix composition, type and quantity of nanoscale reinforcement.
The X-ray analysis of the tribotechnical layer obtained on the basis of the Cu-Al-Fe system with nanoscale ESD tungsten carbides consist of 3,2 – 4,3 mas % WC; 8,97 – 9,56 mas % of aluminum, along the cross section; 3,31 – 2,78 mas % of iron, the width of the transition zone is 20 – 47 μm. Metallographic analysis showed the absence of significant defects (cavities, stratifications, cracks on the edge of the consolidation zone).
The possibilities of the diffusion metallization method and liquid-phase doping by means of furnace surfacing to create a functional composite layer on a steel base with a matrix of CuAl8Fe3 copper alloy composition additionally reinforced with nanoscale particles at temperature 1150 °C for 15-20 min is shown.