Zhenbing Cai

Dual motion fretting wear behaviors of titanium and its alloy in artificial saliva

A dual motion combined by radial and tangential fretting was achieved on a modified hydraulic fretting wear test rig. The dual motion fretting tests of medical pure titanium (TA2) and Ti6Al7Nb alloy in artificial saliva were carried out under varied contact inclined angles (45° and 60°), and the maximum imposed load varied from 200 to 400 N at a constant loading speed of 6 mm/min. The effects of the cyclic vertical force and the inclined angle were investigated in detail. Dynamic analysis in combination with microscopic examinations shows that the wear scar and plastic deformation accumulation present a strong asymmetry. The Ti6Al7Nb has better wear resistance than TA2 in artificial saliva at the same test parameters, and with the increase of inclined angle and decrease of imposed load, the wear reduces accordingly. The wear mechanisms of pure titanium TA2 and Ti6Al7Nb alloy under the condition of dual motion fretting in artificial saliva are abrasive wear, oxidative wear and delamination.

Tribological properties of WS2/graphene nanocomposites as lubricating oil additives

In this study, we prepared a new composite material of graphene (GP) anchored with WS2 nanoparticles (WS2/GP). The lubricating potential of the as-prepared nanocomposites as oil additives was investigated with sliding steel-on-steel contact using a UMT-2 ball-on-plate tribotester. The oil dispersed with WS2/GP displays remarkable lubricating performance; the friction coefficient and the wear rate were reduced by 70.2% and 65.8%, respectively, when 0.02–0.04 wt% WS2/GP was added to the base oil. Its friction-reducing and anti-wear abilities were also superior to those of oil containing a single nanomaterial of GP or WS2 nanoparticles (nano-WS2) and oil dispersed with a physical mixture of nano-WS2 and GP. WS2/GP may deposit on the wear surfaces and form a protective film, which improves the contact state of the sliding interfaces. Moreover, a synergistic lubricating action between the GP and nano-WS2 in the WS2/GP nanocomposites was revealed. We suggest that these two nano-additives cooperatively work, which enhances the adsorption of GP layers and deposition of nano-WS2, thereby resulting in an improved protective and repairing effect.

Effect of nitrogen ion implantation dose on torsional fretting wear behavior of titanium and its alloy

Abstract Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO 2 ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.

Effect of frequency on fretting wear behavior of Ti/TiN multilayer film on depleted uranium

The Ti/TiN multi-layer film was prepared on the depleted uranium (DU) substrate by cathodic arc ion plating equipment. The character of multi-layer film was studied by SEM, XRD and AES, revealed that the surface was composed of small compact particle and the cross-section had a multi-layer structure. The fretting wear performance under different frequencies was performed by a MFT-6000 machine with a ball-on-plate configuration. The wear morphology was analyzed by white light interferometer, OM and SEM with an EDX. The result shows the Ti/TiN multi-layer film could greatly improve the fretting wear performance compared to the DU substrate. The fretting wear running and damaged behavior are strongly dependent on the film and test frequency. The fretting region of DU substrate and Ti/TiN multi-layer under low test frequency is gross slip. With the increase of test frequency, the fretting region of Ti/TiN multi-layer change from gross slip to mixed fretting, then to partial slip.

Experimental Study of the Fretting Wear Behavior of Incoloy 800 Alloy at High Temperature

ABSTRACT The fretting wear behavior of the nuclear power material Incoloy 800 was investigated in this study. A PLINT high-temperature fretting tester was used on an Incoloy 800 cylinder against a 304SS cylinder at vertical cross contact under different temperatures (25, 300, and 400°C). During testing, a normal load of 80 N was applied, and the displacement amplitudes ranged from 2 to 40 µm. The fretting wear mechanism at high temperatures and the kinetic character of the materials of the Incoloy 800 steam generator tube were analyzed. Results showed that the fretting running regimes varied little with ncreasing temperature, and some microcracks were observed in both the mixed fretting regime (MFR) and the partial slip regime (PSR) at high temperatures. Slight abrasive wear and microcracks were the main wear mechanisms of the Incoloy 800 alloy in PSR, whereas those in the MFR and the gross slip regime were oxidative wear, abrasive wear, and delamination.

A Comparative Study on the Fretting Behaviors of Human Femur Compact Bone under Tangential and Radial Fretting Models in vitro

Testes of two fretting modes (i.e. tangential and radial fretting) of human human femur cortical bone against TA2 ball in vitro have been carried out under the varied imposed normal loads. Much severer surface damage occurred at high displacement amplitudes under the testing of tangential fretting than that of radial fretting. Ploughs and detachment of particles were observed in the wear scars of tangential fretting specimens. Combination of abrasive wear and delamination was the mechanism of tangential fretting of cortical bone. The results under radial fretting condition show that circumferential lamella of osteon presented a better resistance than that of interstitial lamella. Micro-cracks and delamination occurred primarily at the edge of contact zone. It was found that Haversian system of cortical bone played an important role under the two fretting modes. Tthe liquid exudant come from the degradation of bone was played an important role as a lubricant.

Fretting Wear Damage Mechanism of Uranium under Various Atmosphere and Vacuum Conditions

A fretting wear experiment with uranium has been performed on a linear reciprocating tribometer with ball-on-disk contact. This study focused on the fretting behavior of the uranium under different atmospheres (Ar, Air (21% O2 + 78% N2), and O2) and vacuum conditions (1.05 and 1 × 10−4 Pa). Evolution of friction was assessed by coefficient of friction (COF) and friction-dissipated energy. The oxide of the wear surface was evaluated by Raman spectroscopy. The result shows that fretting wear behavior presents strong atmosphere and vacuum condition dependence. With increasing oxygen content, the COF decreases due to abrasive wear and formation of oxide film. The COF in the oxygen condition is at least 0.335, and it has a maximum wear volume of about 1.48 × 107 μm3. However, the COF in a high vacuum condition is maximum about 1.104, and the wear volume is 1.64 × 106 μm3. The COF in the low vacuum condition is very different: it firstly increased and then decreased rapidly to a steady value. It is caused by slight abrasive wear and the formation of tribofilm after thousands of cycles.

Antiwear Properties of Bonded MoS2 Solid Lubricant Coating under Dual-Rotary Fretting Conditions

ABSTRACT Bonded MoS2 solid lubricant coatings are widely used in tribology for their friction-reducing and antiwear properties. However, such coatings have been rarely investigated in complex fretting conditions, such as dual-rotary fretting (DRF). DRF is a complex fretting wear mode that combines torsional fretting with rotational fretting. In this work, the antiwear properties of bonded MoS2 solid lubricant coating under dual-rotary fretting conditions were studied. Results indicated that the MoS2 coating had better friction-reducing and antiwear properties than the substrate for alleviating DRF wear. The coating can greatly influence the fretting regimes and reduce the coefficient of friction. Furthermore, the service life of the coating was strongly dependent on the competition of the two fretting components and was reduced as the rotational fretting component increased.

Effect of roughness on electrical contact performance of electronic components

Abstract This study investigated the effects of electrical contact resistance (ECR) on pogo pins used in mobile phones, chargers, digital cameras, Bluetooth headsets, medical equipment, and other electronic products with different surface roughness. Experimental results revealed that metallic wear debris is generated by fretting motion and formation of a third body on rough surfaces without removal by fretting motion, thus increasing ECR. Wear debris does not easily form the third body at contact areas of smooth surfaces and causes formation of metal–metal contact pattern. Results showed low ECR with fretting motion. 3D and 2D profiles of contact area verified the definition of contacting high spots, further explaining increases in ECR.

Modification of Talc@TiO2 toward high-performance nitrile rubber application

To improve the dispersion of talcum powder (Talc) for polymer applications, modified nano-titania powders (TiO2) using a silane coupling agent (KH550), a titanate coupling agent (NDZ201) and sodium polyacrylate (PAAS) were well adhered to the surface of Talc with a ball milling method, thereby preparing a series of mixed Talc@TiO2 particles to realize good dispersion in carboxylated acrylonitrile–butadiene rubber (XNBR). Note that Talc@TiO2 particles modified by PAAS and NDZ201 show better colloidal dispersion in anhydrous ethanol due to organification and repulsion of charge, with original Talc and NDZ201 modified Talc@TiO2 powders as a comparison. Modified Talc@TiO2 hybrid XNBR shows good performance characteristics, including damping capacity and impact resistance, depending mainly on the excellent mechanical property of Talc, good dispersion and the high adhesive force between modified Talc@TiO2 and XNBR.