The influence of operating conditions on the tribological properties of Zn-30Al-3Cu-0.5Si alloy

Purpose The paper aims to investigate the effect of operating conditions on the dry and lubricated wear behaviour of the Zn-30Al-3Cu-0.5Si alloy. Design/methodology/approach Wear tests on Zn-30Al-3Cu-0.5Si alloy samples were conducted under both unlubricated (1–5 MPa, 0.5–5 ms−1, 2500 m) and lubricated (2–7 MPa, 0.5–2.5 ms−1, 20 km, 1 cm3 h−1) conditions using a block-on-disc–type tester. The friction coefficient (FC), temperature (T) and wear volume (WV) were measured as functions of contact pressure (CP) and sliding velocity (SV). Worn surfaces and subsurface microstructures were characterised using scanning electron microscopy (SEM) and microhardness measurements. Findings As CP and SV increased, both the T and WV of the alloy increased under both lubricated and unlubricated conditions. FC decreased with increasing CP but increased with SV, ranging from 0.022 to 0.115 under lubricated conditions and from 0.31 to 0.49 under unlubricated conditions. Correlation analysis indicated that the FC, T and WV of the alloy can be predicted based on CP and SV. Subsurface analysis revealed two distinct layers formed under unlubricated conditions, with microhardness increasing from 95 HV to over 358 HV at higher CP and SV. Adhesion and abrasion were observed to be the dominant wear mechanisms. Originality/value This research provides, for the first time, empirical equations describing the relationships between tribological properties (friction coefficient and wear volume) and operating parameters for Zn-30Al-3Cu-0.5Si alloy under both lubricated and unlubricated conditions. These equations can be used to predict the tribological performance of sliding bearings manufactured from this alloy under the specified conditions.