WEAR AND SEIZURE OF BINARY AL-SI ALLOYS

The wear and seizure behaviour of binary Al-Si alloys containing up to 23% Si has been investigated in sliding against a hard steel counterface by continuous loading experiments carried out in a pin-on-disc machine. Addition of silicon to pure aluminium improves wear and seizure resistance. The wear characteristics of alloys containing 7-17% Si, when considered as a function of load, exhibit distinct mild wear, severe wear and seizure regimes. Mild wear is characterised by the in situ formation of a protective iron-rich compacted layer. The severe wear is initiated when the protective layer is removed as a result of subsurface flow. On further increment of load this leads to seizure. Based on morphological observations in SEM, a qualitative model has been proposed for the wear behaviour of this group of alloys. An alloy containing 23% Si exhibits only mild and severe wear regimes and does not show any seizure within the present experimental limits. The alloy has low thermal conductivity and is prone to plastic flow instabilities as observed in compression tests. Because of these factors, the critical contact temperature required for seizure is not attained under the test conditions.