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This paper aims to study the tribocorrosion and the surface repassivation behaviors of Monel 400 alloy in artificial seawater.

In this study, the tribocorrosion behavior of Monel 400 alloy was studied under different applied loads in artificial seawater by using a pin-on-disk tribometer equipped with an electrochemical workstation. The applied loads were selected ranging from 50 to 200 N. The surface repassivation behavior of Monel 400 alloy was studied by X-ray photoelectron spectroscopy.

It was demonstrated that mass loss was determined by the combined effect of mechanical wear and chemical corrosion. The surface repassivation mechanism of the alloy is that layer corrosion product film formed on the surface of Monel 400 alloy, which can protect metal matrix from future corrosion.

This research adds original content in revealing the tribocorrosion and surface repassivation behaviors of Monel 400 alloy under different loads, which offer a theoretical basis for the application under the corrosion and wear environment of Monel 400.

This paper aims to investigate the influence of scan speed on the corrosion and tribocorrosion features of the CoCrMoW samples fabricated via the selective laser melting (SLM) process.

CoCrMoW samples were produced by SLM at different scan speeds. Produced samples were made via structural surveys (X-ray diffraction examinations and scanning electron microscopic analyses), hardness measurements and electrochemical and tribocorrosion experiments.

Outcomes displayed that the corrosion and tribocorrosion properties of CoCrMoW alloy were significantly influenced by scanning speeds. Also, these properties of the alloy increased with increasing scanning speeds. CoCrMoW samples produced at a laser scan speed of 1,000 mm/s showed the best resistance to corrosion and tribocorrosion. This could be related to the high hardness and low grain structure of the fabricated samples.

This paper may be a practical reference and offers insight into the effect of scanning speeds on the increase of hardness, tribological and corrosion performance of CoCrMoW alloys. This study can help in the further advancement of cobalt-chromium alloy in situ produced by SLM for both electrochemical and tribocorrosion behavior for biomedical applications.

The aim of this work is to study the tribocorrosion behaviors of Hastelloy C276 alloy sliding against AISI 316 stainless steel in artificial seawater and distilled water.

The electrochemical behaviors of Hastelloy C276 alloy are measured by potentiodynamic polarization method. The tribocorrosion properties are evaluated using an MRH-03 type ring-on-block test rig in artificial seawater with different salinity. The wear loss is determined by the difference of sample weight before and after tribocorrosion tests.

The results show that the typical passivation behavior is observed for C276 alloy in seawater. The Hastelloy C276 alloy has the maximum corrosion current density in 3 percent seawater, which is the synergism of salt concentration and dissolved oxygen in seawater. Friction coefficients are in general larger in distilled water compared with seawater. The wear loss in seawater is always higher than that in distilled water for both alloys. Seawater could reduce the friction coefficient and the wear resistance.

Many scientists focused on studying the friction behavior of passive metals sliding against alumina or zirconia, which was considered to act as inert antagonist in the experiments. However, there are few papers available on the tribocorrosion properties of passive metals sliding each other in corrosion mediums.

Ti6Al4V is a widely used metal for biomedical application due to its excellent corrosion resistance, biocompatibility and mechanical strength. However, a coupling reaction of friction and corrosion is the critical reason for the failure of implants during the long-term service in human body, shortening the life expectancy and clinical efficacy of prosthesis. Hence, this study aims to find a feasible approach to modify the service performances of Ti6Al4V.

Selective laser melting (SLM), as one of the emerging metal-based additive manufacturing (AM) technologies is capable for fabricating patient-specific personalized customization of artificial prosthesis joints, owing to its high adaptability for complex structures. This study is concerned with the tribocorrosion behavior of SLM fabricated Ti6Al4V substrate enhanced by laser rescanning and graphene oxide (GO) mixing. The tribocorrosion tests were performed on a ball-on-plate configuration under the medium of simulated body fluid (SBF). Moreover, the surface morphologies, microstructures, microhardness and contact angle tests were used to further reveal the in-situ strengthening mechanism of GO/Ti6Al4V nanocomposites.

The results suggest that the strengthening method of GO mixing and laser rescanning shows its capability to enhance the wear resistance of Ti6Al4V by improving surface morphologies and promoting the generation of hard phases. The wear volume of R-GO/Ti6Al4V is 5.1 × 10⁻² mm³, which is 25.0% lower than that of pure SLM-produced Ti6Al4V. Moreover, a wear-accelerated corrosion of the Ti6Al4V occurs in SBF medium, leading to a drop in the open circuit potential (OCP), but R-GO/Ti6Al4V has the lowest tendency to corrosion. Compared to that of pure Ti6Al4V, the microhardness and contact angle of R-GO/Ti6Al4V were increased by 32.89% and 32.60%, respectively.

Previous investigations related to SLM of Ti6Al4V have focused on improving its density, friction and mechanical performances by process optimization or mixing reinforcement phase. The authors innovatively found that the combination of laser rescanning and GO mixing can synergistically enhance the tribocorrosion properties of titanium alloy, which is a feasible way to prolong the service lives of medical implants.

This paper aims to improve the tribocorrosion properties of 316L, thus WC/Ni60 coated 316L was prepared by thermal spraying technique.

Composition and microstructure of WC/Ni60 coating was investigated, and tribological properties of 316 L and WC/Ni60 coating were studied under dry sliding, deionized water and artificial seawater.

The results showed that WC/Ni60 coating was lamellar structure, and the phase composition consisted of γ-Ni solid solution, carbides and borides. Furthermore, the hardness and corrosion resistance of 316 L in static seawater and wear resistance in dry sliding were improved by WC reinforced nickel-based coating. Furthermore, tribocorrosion results demonstrated that wear resistance of WC/Ni60 coating was also significantly better than 316 L, especially for higher load at artificial seawater. The reason can be attributed to the fact that the passive film of WC/Ni60 coating consisted of tungsten carbide, Ni(OH)2 and FeOOH for WC/Ni60 coating and only FeOOH for 316 L.

According to this study, it can be concluded that WC phases acted as a role in resisting the wear damages. Meanwhile, Ni-based materials performed well in corrosion resistance. Thus, the combined-effect Ni-based alloys and WC phases in WC/Ni60 coating showed better tribocorrosion performance than 316 L.

This paper aims to investigate the structural, corrosion and the study of tribocorrosion features of the AA7075 aluminum alloy with and without the application of electroless Ni-P/Ni-B duplex coating with a thickness of approximately 40 microns.

Surface characterization of the samples was made by structural surveys (light optic microscope, scanning electron microscopic examinations and X-ray diffraction analyses), hardness measurements, corrosion and tribocorrosion tests.

Results of the experiments showed that upper Ni-B coating deposited on the surface of first Ni-P layer by duplex treatment caused remarkable increment in the hardness, corrosion resistance and tribocorrosion performance as compared to the AA7075 aluminum alloy.

This study can be a practical reference and offers insight into the effects of duplex treating on the increase of hardness, corrosion and tribocorrosion performance.

The aim of this work is the study the tribological behaviour and tribocorrosion resistance of newly developed multilayer PVD coatings Cr/CrN and CrN/ZrCN applied on nitrided F1272 steel for gear applications.

Tribological characterization has been completed by several tribological tests performed under ball‐on‐disc configuration, extreme pressure tests to determine the maximum load before the films failure and rolling‐sliding tests under line‐contact conditions (35‐40 per cent of sliding). The response of the different coatings to sodium chloride aggressive environment has been simulated by accelerated tribocorrosion tests, combining simultaneously chemical and mechanical factors. The synergistic effect of wear on corrosion behaviour and vice versa, has been studied in order to compare the protective properties of the different PVD coatings developed.

Cr/CrN PVD coating improves wear in almost a 90 per cent compared to the nitrided substrate, presenting a similar behaviour to this one under extreme pressure conditions. CrN/ZrCN coating also improved substrate wear and especially good behaviour for this coating was observed under extreme pressure conditions. Cr/CrN coating strongly decreases micropitting and scuffing effect when it is tested under rolling‐sliding configuration. Under micro‐pitting conditions, coating protects the substrate and reduces the fatigue of uncoated discs. When adhesive wear (scuffing) is studied also Cr/CrN improves notable the nitrided steel performance. Under simultaneously corrosion‐wear conditions, Cr/CrN coating registered the lowest material loss because in this case only corrosion effect contributed to the coated surface degradation being the mechanical contribution inappreciable.

New multilayer coatings with improved wear performance and tribocorrosion resistance have been developed and comprehensively characterized. These coatings can be used in advanced gears for corrosive environmental conditions as well as with biodegradable lubricants.

This paper aims to study the tribocorrosion behavior of 304 stainless steel (SS) sliding against SiC and Si₃N₄ counterparts in artificial seawater.

The tribocorrosion behavior of 304SS sliding against SiC and Si₃N₄ balls in artificial seawater has been investigated. The tests were conducted using a ball-on-disk rig equipped with an electrochemical workstation. The friction coefficient, surface morphology, wear volume and current density were determined.

When 304SS sliding against SiC ball, a smooth surface with a silica layer was formed on the top, which led to the low friction coefficient, current density and small wear volume. For 304SS-Si₃N₄ tribo-pair, a lot of metal debris was scattered on contact surfaces leading to high friction coefficient, current density and big wear volume.

This research suggests that the lubrication effect of silicon-based ceramics is related to counterpart specimen in artificial seawater.

The results may help us to choose the appropriate ceramic ball under seawater environment.

The main originality of the work is to reveal the tribocorrosion behavior of 304SS sliding against SiC and Si₃N₄ balls, which help us to realize that the Si₃N₄ ball as water-lubricated ceramics could not exhibit lubrication effect when coupled with 304SS in artificial seawater.

This report aims to study the influence of applied potentials on the corrosion-wear behavior of 316L stainless steel (SS) in artificial seawater.

In this study, wear-corrosion behavior of 316L SS had been studied under different applied potentials in artificial seawater by using a reformed pin-on-disc test rig. The applied potentials were selected ranging from –1.2 to 0.3 V (vs Ag/AgCl). The friction coefficient, mass loss rate and current density were determined.

It was indicated that mass loss was determined by the combined effect of mechanical wear and chemical corrosion. The wear-corrosion process was synergistic effects dominate while mechanical wear contributed the major material mass loss.

The results helped us to choose the appropriate metals for application under the specified environment.

The main originality of this research is to reveal the corrosion-wear behavior of 316L SS under different potentials, which would help us to understand different states of 316L SS under different corrosion environments.

This paper aims to investigate the stability of passive oxide film formed on the surface of 316L stainless steel in 3.5 Wt.% NaCl in the presence of two environmentally non-toxic inhibitors, i.e. leaf extracts of Musa spp. (MS) and Jatropha curcas (JC).

Current transients and potentiodynamic polarization curves were used to explain the stability of the passive film on Current transients and potentiodynamic polarization curves were used to explain the stability of the passive film on 316L stainless steel at both ambient temperature (25 °C) and 70 °C. For the potentiostatic tests, the coupons underwent cathodic stripping to remove the native oxide on their surfaces at −850 mV for 600 s, and a potential of 50 mV was imposed to observe the repassivation for 200 s. For the potentiodynamic tests, the pitting potential measured at 100 μA/cm2, corrosion potential and cathodic current density were obtained for analysis.

The current transients perfectly fitted into the exponential decay curve; i = i_s + i_peak exp(−t/τ), where the decay constant, τ measures the repassivating speed and extent to which the newly formed film heals and stabilizes. The current transients showed that MS and JC help in the repassivating process, especially at 300 ppm and 200 ppm, respectively, both at the lower temperature. The potentiodynamic curves mostly correlated with the current transients except for the hybrid inhibitor. The inhibitors increased the pitting potentials at concentrations that are correlated to their scanning electron micrograph images.

Because they are cheap and environmentally friendly, plant extracts that are proven corrosion inhibitors could be used to aid the formation of passive film on passive alloys in not-so-aggressive environments.

Both MS and JC improve the film stability mostly at intermediate concentrations of 200 and 300 ppm, respectively, at ambient temperature and 70° C.

Using leaf extracts of plants as green inhibitors is considered an environmentally friendly engineering solution.

The leaf extracts are a convenient resource of green inhibitors because their plants are readily available or could be easily naturalized, the processing technique to obtain the extracts is very cheap and the inhibitors are environmentally friendly. In addition, cathodic stripping exposes a relatively larger surface area than that obtained using the most common forms of depassivation; hence, the efficiency of the inhibitor in aiding the formation of the new oxide film to cover the bare surface would be better measured. There is very lean research data on the combined use of green inhibitors and cathodic stripping to study repassivating kinetics of passive alloys.