Tribological Investigation of Wear Behavior and Mechanisms in B390 and Sr-Modified B390 Aluminum Alloys under Dry and Wet Conditions

Wear-resistant, die-cast B390 aluminum represents a relevant material frequently used in the automotive industry. The wear and its relation to the microstructure along with different alloying additives is studied with efforts toward improved performance. Alloying by Sr allows for a lower Fe content helps in mitigating iron needling. This paper addresses wear performance of B390 and Sr-modified B390 alloys, tested against pearlitic cast iron, used for manufacture of piston rings. The wear tests were designed by using an ASTM G99 standardized pin-on-disc protocol at “wet” (motor oil) and “dry” conditions and were performed using a UMT (Bruker) benchtop tester. The polished cross-sections and friction surfaces were studied to identify the microstructural differences and dominating wear mechanisms. Interestingly, the stronger and harder Sr-modified B390 alloys wear more at dry conditions compared to the standard die-cast B390 alloy. This was ascribed to a change in wear mechanisms of the developed friction layer, which had a considerable impact on the observed friction and wear levels, compared to the observed microstructural differences. Also, the presence of thin liquid film under wet testing conditions helped in controlling the material–lubricant interaction and in achieving lower friction levels.