Improving mechanical and tribological performances of pure copper matrix surface composites reinforced by Ti2AlC MAX phase and MoS2 nanoparticles

Multiple passes of the friction stir processing (FSP), were applied on the pure copper substrates. As reinforcements, Ti2AlC and MoS2 nanoparticles were employed for developing pure copper matrix surface nanocomposites. To investigate the microstructural evolution of the samples upon the FSP, optical microscopy (OM) and scanning electron microscopy (SEM) were utilized. Considerable microstructural grain refinement was achieved in the samples subjected to the FSP. To evaluate the hardness of the samples, the Vicker's microhardness method was used. Accordingly, the average microhardness of the Cu/MoS2 and Cu/Ti2AlC nanocomposites increased by about 38% and 55%, respectively, as compared to the non-reinforced sample. The samples were further subjected to uniaxial tensile test to assess their mechanical properties. The ultimate tensile strength (UTS) values of the base metal (BM) and Cu/Ti2AlC nanocomposite samples subjected to 4-pass FSP, were improved by nearly 75% and 175%, respectively. To investigate the tribological behavior of the samples, the dry sliding wear test was carried out by the AISI 52100 steel counterpart. The mass losses of the Cu/MoS2 and Cu/Ti2AlC nanocomposites were about half of the pure copper base metal, and the average friction coefficient decreased by 20% and 32% for the Cu/Ti2AlC and Cu/MoS2 nanocomposites, respectively. SEM investigations on the worn surface and the debris generated by the wearing of the samples after the 300 m sliding wear test, indicated the occurrence of the adhesion and delamination mechanisms in the case of the non-reinforced samples, while abrasion and delamination were the dominant mechanisms for the composites samples.