Effectiveness of high-frequency ultrasonic peening treatment on the tribological characteristics of Cu-based sintered materials on steel substrate

The effects of high-frequency ultrasonic peening (HFUP) on the tribological characteristics of Cu-based materials sintered on low carbon steel by a powder metallurgy (P/M) technique were investigated. The friction and wear properties of the Cu-based materials were studied using a pin-on-disk reciprocating tribotester sliding against a hardened steel ball under dry and oil-lubricated conditions. Scanning electron microscopy (SEM) was utilized to analyze the worn surfaces and to assess the wear mechanisms. Experimental results showed that the HFUP process led to a reduction in friction and wear of the Cu-based materials in both dry and oil-lubricated conditions. This was attributed to the increase in hardness of the HFUP treated specimen. It was also found that the friction coefficient was independent of the normal load but decreased with increasing sliding speed. In addition, inclusion of Fe in the Cu-based material was helpful in reduction of friction and wear. SEM analyses showed that abrasive wear was the dominant wear mechanism of the specimens. The results of this work demonstrate the effectiveness of HFUP in improving the tribological properties of Cu-based materials.