Microstructure and wear resistance of direct laser-deposited TiC-enhanced aluminum-based composite coating for brake discs

Abstract

To prepare a wear-resistant coating on the surface of aluminum alloy to replace cast iron to realize the lightweight of the urban rail transit brake disc is a promising and low-cost method. In this work, aluminum-based composite coatings reinforced with TiC particles of different mass percentages (20 %, 40 %, 60 %) were successfully prepared on the surface of 2A70 high-strength aluminum alloy by direct laser deposition technology. The microstructure of the coating was analyzed, and the high-temperature wear resistance of the coating was studied and compared with that of the substrate. The “stirring” effect of TiC particles on the molten pool could effectively reduce the porosity defects. The 40 %TiC coating has the highest shear strength. The main phases in the coating are α-Al and TiC, and the diffusely distributed TiC particles effectively prevented the foreign matter from pressing into the coating, thus improving the wear resistance of the coating. The 20 %TiC and 40 %TiC coatings mainly occurred in abrasive wear and adhesive wear at different temperatures, while the 60 %TiC coating mainly occurred in fatigue wear with more spalling pits on the wear surface and the largest wear rate. The 40 %TiC coating shows the most excellent wear resistance.