The influence of strontium addition on the tribological properties of Zn25Al3Si alloy in boundary lubricated condition

Abstract

The zinc-aluminium based casting alloy ZA-27 is well-established alloy and is frequently used materials for sleeves of plain bearings. It has good physical, mechanical and tribological properties. However, one of the major disadvantages is its dimensional instability over a period of time (ageing). To overcome this, the copper in the alloy may be replaced by silicon. Coarsening of the silicon particles is controlled by suitable additions of strontium. The influence of the strontium addition on friction and wear properties in boundary lubricated conditions was done on block-on-disc tribometer. The tests were carried-out for three Zn25Al3Si alloys with variable strontium content (0 wt. %, 0.03 wt. % and 0.05 wt. %), and, for the purpose of comparison, for standard ZA-27 alloy. Tests have confirmed that the wear rate of zinc-aluminium alloys with silicon is lower than the standard ZA-27, and have shown that the strontium addition lowers that rate additionally, with the slight increase of the coefficient of friction.