Wear behavior, microstructure, and dimensional stability of as-cast zinc-aluminum/SIC (metal matrix composites) alloys

Abstract

The wear behaviors of five different zinc-aluminum (ZA)-based alloys containing silicon, copper, and 8 and 16 pct on volume of reinforcing silicon carbide (SiC) particles were analyzed. Hardness, dimensional stability, and wear tests were performed on these five alloy samples. Microstructural investigation and semiquantitative chemical analysis of the different alloying characteristics of the cast samples, the wear surface, and the wear debris were obtained by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDXA), and X-ray diffraction (XRD). The addition of Si, Cu, and SiC has a significant effect on the solidification process and final morphology of the alloys. The five cast alloys tested showed dimensional stability for a period of 1000 hours at 165°C±2.5°C. The wear tests were performed using a pin-on-disc apparatus under dry and lubricated conditions. Loads of 29.43 N (3 kg), 49.05 N (5 kg), and 78.48 N (8 kg) and a velocity of 250 rpm (2 m/s) were used. The results indicate that the wear rate of ZA alloys is strongly dependent on test load in a non-linear relationship and that the addition of SiC particles improved the wear properties of the matrix alloys. Under dry conditions, there was considerable loss of material, particularly in the nonreinforced alloys. In addition, the nonreinforced alloys presented substantial local plastic deformation and transfer of elements between the disc, the sample, and the debris. The amount of element transfer can be correlated with the elements presented. The proposed wear mechanisms are discussed.