Mild Sliding Wear of Fe–0.2%C, Ti–6%Al–4%V and Al-7072: A Comparative Study

Abstract

The mild sliding wear of Fe-0.2%C, Ti-6%Al-4%V and Al-7072 was investigated by means of pin-ondisc sliding tests. The applied pressure was 1 MPa and the sliding velocity was varied between 0.2 and 1 m/s. The sliding behaviour was followed by continuous measurements of the friction coefficient, pin wear and pin temperature. For the Fe alloy, wear was mixed (delamination and oxidation), and friction and wear coefficients were found to decrease with sliding velocity. The Al and Ti alloys displayed a different behaviour, characterised by the occurrence of sliding distance transitions at 0.8 and 1 m/s for the Al alloy, and at 0.4 up to 1 m/s for the Ti alloy. Before the transition, the wear coefficient of the Al alloy was very low, because of the presence of a compacted tribolayer on the sliding surface. After the transition wear was by delamination: the wear rate increased but the friction coefficient decreased. For the Ti alloy, wear occurred by oxidation and was quite high before the transition. After the transition, both the wear rate and the friction coefficient decreased, although the wear process became unstable with repeated oscillations in the friction coefficient. The results allowed us to highlight the role of flash temperature in determining the wear mechanisms of the alloys under study and the necessity of properly considering the sliding distance transitions to make reliable comparisons and obtain guidelines for safe operations.

Effect of microstructural evolution on wettability and tribological behavior of TiO2 nanotubular arrays coated on Ti–6Al–4V

“…Ti-6Al-4V alloy is reported to have notoriously poor wear resistance due to its low resistance to plastic shearing and the low level of protection imparted by surface oxides [10]. Recently, research on the tribological properties and mechanisms of Ti-6Al-4V alloy under different sliding speeds and loads was conducted [11,12]. According to these studies, a transition from oxidative wear to delamination wear occurred with an increase in sliding speed and that low wear resistance was due, in part, to the weak protection afforded by surface oxides.…”

Wear Mechanisms

“…4.4. The reported observations refer to a titanium alloy (Ti-6Al-4V) after dry sliding against a steel counterface [7,8]. The occurrence of large shear plastic deformation (by ratcheting/low cycle fatigue) at the asperities can be clearly appreciated in Fig.…”

“…Such a stress can induce the formation of a wear fragment by brittle contact, if the material has sufficiently low fracture toughness [10]. Consider, for example, the contact between a sphere and a [7,8] plane. Combining Eqs.…”

Materials for Tribology

“…As an example, Fig. 6.13 shows the morphology of the wear debris (a) and of the worn track (b) in the case of an Al-7072 alloy after dry sliding at 1 MPa and 0.2 m/s against an AISI 52100 steel [26]. The fragments appear to be small and equiaxed; they originate from the brittle fragmentation of the tribolayer, i.e., from regions 2 in Fig.…”