Characterisation and tribological behaviour of zinc-aluminium (Zn-Al) alloy under dry sliding reciprocating ball on disk tribometer

The frictional behaviour of Zn-Al alloy was investigated under dry sliding (without lubrication) environment subjected to reciprocating action of ball on disc tribometer. Wrought Zn-Al alloy sample was received as cylindrical rods. The obtained wrought Zn-Al alloy samples were grinded and polished to 0.2 lm mirror-like surface finishing. The hardness was measured from the HV/0.5 indentation tests with a normal load. The phase examination of the Zn-Al alloy material was done by x-ray diffraction (XRD) while the chemical composition was determined by x-ray fluorescence (XRF). A 6.00 mm diameter alumina ball was rubbed against the surface of the Zn-Al alloy samples under increasing normal loads (1, 3, 5 and 10 N) at room temperature and atmospheric humidity. The morphologies of the as received and worn surfaces were examined using high resolution metallurgical optical microscope (OM) and scanning electron microscope (SEM). The CoFs were obtained under dry sliding reciprocating ball on disk tribometer with the InstrumX 7.3.13 version software. The results show that Zn-Al alloy has average hardness of HV/0.5 of 54.4 and average CoFs of 0.1591, 0.413, 0.0739 and 0.4793 under the 1, 3, 5 and 10 N applied loads respectively. Generally, there are slight similarities in the trend CoF - time curves for Zn-Al alloys subjected to small range of frictional loads. There is lower wear resistance due to significant effect of high content of about 98 %Zn in Zn-Al alloy which reduced sliding wear resistance for the Zn-Al alloy as compared with the 1.79 ~ 0.001 %Zn in the cast A6061 and AlSi alloys previously reported.