Wear behavior of A356/M₇C₃ and A356/SiC particulate metal matrix composites

The stability of M₇C₃ carbides as reinforcement for A356 materials for tribological applications has been investigated. For this purpose, A356/M₇C₃, A356/SiC and A356/M₇C₃/SiC composites were prepared by powder metallurgy and tested at room temperature against SAE 4620 steel ring and AISI 304 stainless steel counterfaces under loads of 10-150 N. For comparison, also unreinforced A356 specimens were processed and tested under the same conditions. The tribological behavior was evaluated by microstructural examination of the wear-effected zones and by weight loss measurements of the specimens and counterfaces. The wear behavior of A356/M₇C₃ composite gave an excellent result as function of the applied load because the M₇C₃ particles act as load-bearing elements due to their excellent bonding to the Al matrix, and their interfaces withstood the wear stresses even at the highest applied load. Moreover, the M₇C₃ particles limited the incorporation of wear debris into the Al matrix and reduced the wear damage occasioned to the steel counterfaces compared to that of A356 Al alloy.