In this study, using a self-made impact test rig controlled by the electromagnet and the time relay, a steel ball in an upper clamp is impacted on to 40Cr testing specimens fixed in a lower clamping fixture reciprocatingly. Three contact conditions are employed: dry contact and two lubricated contacts. One lubricant with lower viscosity and the other with higher viscosity were employed in the experiments to study the influence of the viscosity. After experiments, the impact dent is measured by SEM and a surface profiler. The results show that in the dry contact, the repeated impact firstly forms a hardened layer on the metal surface which is damaged in the following impacts. Using the low viscosity oil, the plastic deformation can be restrained effectively. Moreover, using high viscosity oil, the dent can be effectively protected from plastic deformation and impact wear if the lubricant is supplied fully. However, if the lubricant is not supplied fully, a long and sharp local dent is produced in the impact dent, resulting in further damage to the metal.
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