Dry sliding wear behavior of globular AZ91 magnesium alloy and AZ91/SiCp composites

Dry sliding wear behavior of rheocast AZ91 magnesium alloy and AZ91/SiCp composites reinforced with 5 and 10 vol% SiC particles were investigated under normal loads of 10-250 N and sliding speeds of 0.1, 0.3, 0.5 and 1 m/s using pin-on-disc configuration against a 1045 steel disc counterbody. In this work, rheocast alloys and composites have been tested to determine the role played by the globular microstructure, and to evaluate if the increase observed in other mechanical properties is also translated to wear behavior. Wear rates and friction coefficients were registered during wear tests. Worn tracks and wear debris were studied by Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Spectrometry (EDS) in order to obtain the predominant wear mechanisms maps of the studied materials. The following wear mechanisms were found in the worn surface of the three materials: abrasion, oxidation delamination and melt wear. The composites with globular microstructure exhibit slightly superior wear resistance at low testing sliding speeds (0.1 and 0.3 m/s) and medium loads (40-80 N) than the AZ91 Mg alloy. But, for other conditions, the presence of SiC particles seems to be detrimental to the wear behavior of AZ91 magnesium alloy. A wear mechanisms map that allows identifying the main wear mechanisms for each wear condition and material composition has been developed. Rheocast microstructure improves the wear resistance of alloys in most conditions but the addition of SiCp reinforcement is only favorable in few of them.