Mechanical and tribological characteristics of sintered Fe-Ni-Cr alloy subjected to high-frequency ultrasonic peening

In this paper, Fe-Ni-Cr alloy friction test specimens were prepared by direct metal laser sintering (DMLS); some specimens were further treated by hot isostatic pressing (HIP) at 1,050°C and 1,150°C in order to reduce the porosity and increase the density of the specimens. Some of the HIP-treated specimens were subjected to high-frequency ultrasonic peening (HFUP) with the aim of improving their tribological properties. Wear tests were performed on a tribometer with a ball-on-disk configuration under dry conditions, while nanoscratch tests were performed using the ultra nanoscratch testing (UNST) technique. The objective of this study is to investigate the effects of the HFUP technique on friction reduction and wear resistance of the DMLS- and HIP-treated Fe-Ni-Cr alloy specimens. The results of the friction and nanoscratch tests showed that the friction coefficient and wear resistance of the HFUP-treated specimens were lower and higher than those of the polished specimens, respectively. However, these results showed that the tribological properties of HFUP-treated specimens were dependent upon the temperature condition of the HIP process. The microstructural characterisation was conducted by optical microscope (OM) and scanning electron microscope (SEM).