Tribological Properties of Sintered Al–Sn Alloy Doped with Iron

Antifriction alloys of the Al–Sn system are widely used as coatings for plain bearing inserts, to increase the strength of which dispersion hardening is used. A mixture of the Al–7Fe–38Sn composition (wt %) from elemental Al, Sn, and Fe powders was sintered in vacuum for 1 h at temperatures below (570°C) and above (710°C) the melting point of aluminum. Then, the sintered cylindrical briquettes with a diameter of 20 mm were additionally compacted at 250°C and ~300 MPa by double-sided compression in a closed mold with a channel of the same diameter. The mechanical properties of the prepared composites were determined by their compression test. Tribological tests of the composites were carried out according to the "pin-on-disk" scheme using a Tribotechnic tribotester (France). At both sintering temperatures, a composite material with tin interlayers and agglomerates of tin-cemented small aluminides located between aluminum grains was found to be formed. The composite prepared by sintering the mixture with iron nanoparticles has the maximal strength and wear resistance under dry friction against a steel disc. It was found that hard particles in composites of the Al–Sn system with a high content of the soft phase can be used as an effective means of increasing the wear resistance if they are uniformly distributed along the matrix grain boundaries during the preparation of the composite. In this case, the particles effectively prevent the localization of deformation in the tin interlayers separating the grains. As a result, the gradient of deformation of the material in the subsurface layer decreases. Thus, the time of wear particles formation and, consequently, the wear resistance of composites of the Al–Sn system increase. With an increase in pressure on the friction surface, the wear intensity of the composite samples increases and the value of the friction coefficient decreases.