Effects of surface nanocrystallization on tribological properties of 316L stainless steel under MoDTC/ZDDP lubrications

• The effects between nanocrystalline layer and MoDTC/ZDDP were investigated.
• Layer with a thickness of 150 μm and a hardness of 340HV0.05 was formed.
• Better friction reduction and wear resistance were exhibited on nanocrystalline layer.
• Higher MoS2/MoO3 ratio and surface reactivity contributed to the lowest COF.
• The best antiwear was attributed to hard layer and shorter polyphosphate.

In this paper, 316L stainless steel (316LSS) is treated by a ultrasonic cold forging technology (UCFT) which is one of the methods of surface nanocrystallization. The tribological properties of UCFT sample are investigated by a SRV tribometer under lubrications with MoDTC and ZDDP. The chemical analysis of tribofilms is performed using X-ray photoelectron spectroscopy (XPS). The results show that the UCFT sample exhibits the lowest coefficient of friction (0.066) under MoDTC lubrication and the lowest wear rate under ZDDP lubrication, indicating that surface nanocrystallization has synergistic effects on low friction and antiwear performances of both MoDTC and ZDDP. The obviously synergistic effects between UCFT steel and MoDTC/ZDDP may be attributed to the higher hardness and surface reactivity of the UCFT surface.