Iron Effect on the Tribotechnical Properties of Sintered Al–Sn Alloys

Abstract

The investigated materials were prepared via sintering a mixture of Al, Sn, and Fe elemental powders under vacuum conditions for 1 h at a temperature of 710°C and subsequent compaction in a closed pressing mold at a pressure of about 300 MPa and a temperature of 250°C. The structure of the obtained Al–Fe–Sn composites is represented by an aluminum matrix with the inclusions of FeAl₃ particle agglomerates bound between each other by tin interlayers. Then, the materials were tested for wear resistance under the conditions of dry friction against a rotating disk made of strengthened 40Kh grade steel. The testing was carried out according to a pin-on-disk scheme using a Tribotechnic tribotester (France), the applied pressure varying from 1 to 5 MPa, the sliding velocity of the disk was 0.6 m/s. It was found that adding iron to the Al–Sn alloy provides a significant decrease in the wear rate of the steel disk, but less significantly affects the wear resistance of the samples based on the aluminum matrix. The Al–9Fe–13Sn composite containing about 31 vol % of FeAl₃ and 20 vol % of Sn exhibits the highest wear resistance. Increasing or decreasing tin concentration compared to the mentioned value leads to a decrease in the wear resistance of the investigated materials. A similar effect is caused by an increase or decrease in the iron concentration. It has been found that in the course of dry friction, a thin highly deformed layer that actually consists of oxides including iron oxides transferred from the disk is formed on the surface of Al–Fe–Sn samples. The matrix grains and tin interlayers located under the upper oxide layer are flattened and stretched in the sliding direction. A part of wear particles formed on the sample surface stick onto the steel disk surface in the form of hard adhering particles that cause an intense deformation of the sample surface. The wear mechanism of aluminum matrix composites with a high concentration of iron and tin phases is under discussion.