Investigation of the surface of antifriction Al–Cu–Si–Sn–Pb aluminum alloys

Abstract

The tribological and mechanical properties of Al–Cu–Si–Sn–Pb alloys are studied. The effect of different alloying elements on the structure of their surface and its tribological properties is estimated. The alloys are studied at different stages of their production, i.e., after casting and homogenizing annealing. The character of surface transformations under friction simulated on fiction machines is investigated. The surface is visualized by means of optical and scanning probe microscopy and scanning electron microscopy combined with elemental analysis. Great amounts of oxygen leading to the formation of oxide particles with abrasive properties are revealed on the contact surfaces. The mass transfer of chemical elements also occurs in the contact area: the material of an insert “spreads” over the shaft to form a film of secondary structures. At small thicknesses, this film serves as a solid lubricant, but might promote the formation of scoring during the development of microrelief. The application of two hardness measurement methods, such as “microindentation” and “nanoindentation”, give mutually complementary results. The highest mechanical properties (hardness, up to 0.5 GPa) are established to be attained in silicon- and copper-containing alloys. Homogenizing annealing at 400°C is also revealed to decrease the hardness, but improve the plasticity, which is important for antifriction materials.