Abstract
To improve the fretting damage (fretting wear and fretting fatigue) resistance of Ti-811 titanium alloy, three Cu/Ni multilayer films with the same modulation period thickness (200 nm) and different modulation ratios (3:1, 1:1, 1:3) were deposited on the surface of the alloy via ion-assisted magnetron sputtering deposition (IAD). The bonding strength, micro-hardness, and toughness of the films were evaluated, and the effect of the modulation ratio on the room-temperature fretting wear (FW) and fretting fatigue (FF) resistance of the alloy was determined. The results indicated that the IAD technique can be successfully used to prepare Cu/Ni multilayer films, with high bonding strength, low-friction, and good toughness, which yield improved room-temperature FF and FW resistance of the alloy. For the same modulation period (200 nm), the micro-hardness, friction, and FW resistance of the coated alloy increased, decreased, and improved, respectively, with increasing modulation ratio of the Ni-to-Cu layer thickness. However, the FF resistance of the coated alloy increased non-monotonically with the increasing modulation ratio. Among the three Cu/Ni multilayer films, those with a modulation ratio of 1:1 can confer the highest FF resistance to the Ti-811 alloy, owing mainly to their unique combination of good toughness, high strength, and low-friction.
Highlights
Characterised by high specific strength and excellent mechanical properties, titanium (Ti) alloys are important materials for space and aeronautic applications [1,2]
Nithe monolayer is approximately and the Cu/Ni multilayer films are all harder than the pure Cu film
The Ni monolayer is approximately three times harder than the Cu monolayer, and the Cu/Ni multilayer films are all harder than the pure Cu film
Summary
Characterised by high specific strength and excellent mechanical properties, titanium (Ti) alloys are important materials for space and aeronautic applications [1,2]. These alloys suffer from fretting fatigue (FF) damage, owing to their low thermal conductivity and high coefficient of friction. This can affect the safety and reliability of Ti components [3,4]. FF damage depends on the fretting wear (FW) and fatigue resistance of the material, and surface modification or coating is considered a promising method for combating this damage in Ti alloys. Many attempts, including methods such as shot peening, laser shock processing, low plasticity burnishing, plasma alloying, ion irradiation, physical vapour deposition (PVD), thermal spraying, and ion beam enhanced deposition, have been made to improve the FF properties of Ti alloys [6,7,8,9]
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