Railway Research Institute, Moscow, Russia:

A. E. Mironov, Leading Specialist
I. S. Gershman, Chief Specialist, e-mail: isgershman@gmail.com
E. G. Kotova, Post-Graduate Student
E. I. Gershman, Researcher of Laboratory of Non-Ferrous Metals and Tribology

The changes in the values of hardness and impact elasticity of eight experimental antifriction alloys Al – Sn – Pb – Cu – Si – Zn – Mg – Ti after natural aging and heat treatment are considered. Investigations were carried out for the purpose of development of optimal modes of heat treatment of casting aluminium alloys, intended for the change of casting antifriction bronzes in monometallic plane bearing. Eight experimental casting aluminium antifriction alloys in high complex of tribotechnical properties were investigated. These alloys have higher score resistance, running-in ability, wear resistance and steel counterface wear, than antifriction bronzes. The inclination of all tested alloys to natural aging was defined. Natural aging leads not only to the change of properties, but also to the change of sizes of the finished products. This may lead to the reduction of oil clearance in the plane bearing and, as a consequence, to score. Avoiding such emergency situation requires the artificial aging. The annealing temperature varied from 250 to 350 ^oC, and the annealing time — from 3 to 24 hours. Natural aging was controlled during a year. Annealing at 250 ^oC for 3 hours provides the level of properties achieved by the alloys after 6 months of natural aging. Increasing of annealing temperature to 300 and 350 ^оС overages the alloys. Hardness, ultimate strength, specific elongation, impact elasticity were compared during the heat treatment process. Annealing during 250 ^oC with holding in this temperature during 3 hours is the optimal mode of heat treatment. Artificial aging leads to increasing of stability of alloy properties. There is almost no natural aging after artificial one.

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