Metal Matrix Composite Hardfacing of MIC-6(R) Al Castings by Friction Stir Fabrication

MIC-6(R) and other Al alloys are relatively soft in comparison to other materials used for wear surfaces such as hardened steels and other iron-based materials. However, if the wear resistance of Al castings can be improved by local surface modification then significant weight reductions could be realized by replacing iron-based castings with Al. Deposition of Al-50 vol% SiC coating onto a MIC-6(R) substrate was demonstrated using friction stir fabrication (FSF). While fundamentally a coating process, FSF can be used to successively build-up layers and thus enables true wrought-metal fabrication. The metal matrix composite (MMC) coatings produced in this effort show much promise for the application of FSF to deposit wear resistant coatings onto Al substrates. Microstructural characterization shows a banded structure that is free of defects. Hardness testing showed that the deposited MMC coating is approximately twice as hard the base metal. The MMC coated surface showed an almost three-fold improvement in the reciprocal wear rate as compared to the base casting when tested under ASTM G65 abrasion testing.