Influence Of Casting Procedure On Wear Of Magnesium Matrix Composites Reinforced With Carbon Open-Celled Foam

In this article the characteristics of the macrostructure, microstructure (LM, SEM) and selected properties of magnesium matrix composites reinforced with carbon open-celled foam with a porosity of 10 ppi, obtained by two casting techniques - gravity casting and pressure infiltration, were presented. The open porosity and hardness of the composites were determined. Tribological examinations in dry friction conditions were performed by the pin-on-disc method, and the coefficient of friction, weight loss of the sample as well as the cast iron countersample were determined, and the wear trace was characterized. Observations of the examined material surfaces after friction tests were conducted by SEM. In comparison to the gravity cast composite, a lower porosity, higher hardness and finer magnesium matrix size were found for the pressure infiltrated composite. The impact of the casting technique also concerned the tribological properties. Both the composites exhibited a lower coefficient of friction in comparison to pure magnesium, but for the pressure infiltrated composite the coefficient of friction, weight loss of the sample and countersample, as well as the depth of the wear trace were the lowest. Moreover, after the friction tests, different effects were observed on the surfaces. In the gravity cast composite the carbon component cracked and separated from the matrix, in contrast to the pressure infiltrated composite where uniform wear was observed while maintaining continuous bonding with the matrix, which explains the differences in the tribological properties.