EFFECT OF VACUUM HOT PRESSING TEMPERATURE ON THE MECHANICAL AND TRIBOLOGICAL PROPERTIES OF THE Fe—Cu—Ni—Sn—VN COMPOSITES

Abstract

The mechanical (hardness and elastic modulus) and tribological (friction force and wear rate) properties of the Fe—Cu—N—Sn—VN composites produced by cold pressing and subsequent vacuum hot pressing at different temperatures are studied. The starting iron, copper, nickel, and tin powders have 550 µm particles and the vanadium nitride powder has 0.1—0.7 µm particles. When vacuum hot pressing temperature rises from 800 to 1000 °С, the hardness increases from 3.75 to 5.37 GPa and the elastic modulus decreases from 176 to 125 GPa. As a result, the friction force reduces from 115 to 80 mN and the wear rate from 1.93•10^–5 to 0.45 • 10^–5 mm³ • N^–1 • m^–1. The reasons for improving the mechanical and tribological properties of the sintered composites are discussed. In particular, the main reason for improving the composite's mechanical properties is that the grains refine from 5—50 µm to 20—400 nm through the α→ γ→ α transformation when VN dissolves in α-Fe. In this case, the composite consists of a supersaturated solid solution of nitrogen and vanadium in α-iron, intermetallic Cu₉NiSn₃, and primary and secondary particulate vanadium nitride phases. A relationship between the structure and mechanical and tribological properties is established. The H/E and H³/E² parameters that describe the elastic deformation resistance and plastic deformation resistance correlate with the wear resistance. The sintered composites are considered promising materials for developing a new generation of diamond-containing composites for stone processing industry.