Tribological properties of hybrid aluminum matrix syntactic foams

• Comparison of dry and lubricated wear behavior of metal matrix syntactic foams.
• Tribological effects of different hollow sphere grades in syntactic foams is proposed.
• A correlation between COF and volume fraction of hollow sphere grade is proposed.
• Changes in surface and subsurface structure for syntactic foams are proposed.

Hybrid syntactic foams with AlSi12 aluminum alloy matrix were produced by low pressure infiltration and the wear properties were investigated by pin-on-disc method against a low carbon steel disc counterpart. As reinforcement iron (GM; ~Ø1.9 mm) and two ceramic type (GC; ~Ø1.4 mm and SLG; ~Ø0.12 mm) hollow spheres were used. The volume ratio of GM-GC hollow spheres varied and also SLG+GC hybrid composites were produced. The tests in lubricated condition showed significantly different properties to the dry tests, due to the different oil reservoir capacity of the open hollow spheres in the contact zone, depending on the reinforcement type and ratio. The coefficient of friction, specific wear, height loss and surface damage of the specimens were strongly dependent on the reinforcement type.