Nano-indentation mapping of fretting-induced surface layers

Abstract

Tribologically modified surface layer results from the energy dissipated in the frictional contact area. This layer usually has a different elastic modulus and hardness from the substrate, and its structure corresponds to the intermediate stage between a material of the first-body and debris of the third-body. Even though, the existence of the tribologically transformed structure in the fretting contact has been well proven, the formation and mechanical transformation mechanisms are still not clear. Hence, in this paper, evolution of mechanical properties of four metallic materials (titanium alloy, stainless steel, carbon steel, copper alloy) induced by fretting was investigated using nano-indentation mapping of the fretting wear scars. It was shown that the tribologically transformed structure formed very quickly within the initial fretting cycles, and its mechanical properties remained almost constant during the entire test duration for tested materials. However, it was observed that all materials responded differently to the frictional energy, exhibiting particular rate of change of the H/E ratio before and after the fretting experiment. Modified XRD technique was used to probe the friction induced changes within the small spots of the fretting scars, and revealed distinctive structural modifications within the transformed layers. The approach proposed in this study can be used to inform the predictive 2 wear models, by providing information about the evolution of the mechanical properties of the tribo-system with time.

Tribological performance of graphite-like carbon films with varied thickness

“…Fretting wear was carried out using fretting device with a dedicated electrodynamic shaker as reported in [30][31][32]. All experiments were conducted in dry conditions at 5Hz frequency and ±100 m displacement amplitude.…”

Dynamic changes of mechanical properties induced by friction in the Archard wear model

“…It was found that the TTS nucleated relatively quickly, and after 100 cycles a TTS layer of 100 µm thickness was observed. In order to analyse the evolution of the TTS layer quantitatively, the dissipated energy approach and fretting maps method were proposed [24,25]. It was also found that the increase of hardness during fretting can be related to the strain-hardening in metals [25].…”

“…In order to analyse the evolution of the TTS layer quantitatively, the dissipated energy approach and fretting maps method were proposed [24,25]. It was also found that the increase of hardness during fretting can be related to the strain-hardening in metals [25]. Strain-hardening occurs during plastic deformation, which is induced by the dislocation and twinning of metal crystals [26,27].…”

Fretting wear behavior of duplex PEO/chameleon coating on Al alloy

“…Fretting is a small amplitude oscillatory motion wear process between two bodies leading to progressive surface damage by inducting sub-surface material transformations [18].…”