•Tribocorrosion behaviour and mechanism of S31254 steel were investigated in seawater.•Continual rubbing made the repassivation of contact surface impossible.•Degradation of S31254 steel strongly depended on its corrosion rate.•Abrasion, adhesion and plastic deformation were the predominant wear mechanism.Tribocorrosion is an irreversible transformation of materials and often causes the premature failure of engineering components. In this work, the tribocorrosion behaviour of S31254 steel was investigated on a pin-on-disc tribometer at 50 N, 0.24 m s−1. In seawater, there existed a synergy between corrosion and wear, and this synergy was controlled by potentials through deteriorating the characteristics of the contact surfaces. Especially at +0.3 V, pitting corrosion occurred on metal surface, and the generated pits became the preferred locations of wear and tear, leading to a great synergy and accelerated materials loss rate. Combining X-ray microanalysis with the morphologies of the contact surfaces, the features of abrasive wear, adhesive wear, delamination and plastic deformation were revealed. Quantitative analysis shows that mechanical and corrosion-accelerated wear determined the total mass loss of S31254 steel during tribocorrosion at different potentials.

•Compared the wear behaviors of six polymers under sliding and fretting conditions.•The wear mechanisms at the two test conditions were analyzed in detail.•The microstructure-tribological property relationships of materials were discussed.This work comparatively studied the friction and wear behaviors of the six polymers (UHMWPE, PTFE, Phenolic, PHBA, PEEK and PI) under reciprocating sliding and fretting wear conditions. Hopefully, the results could contribute to provide some guidance for use and selection of materials. By investigating their friction and wear values, the morphologies of the worn surfaces and microstructures, the corresponding wear mechanisms under the two wear modes were analyzed in detail. It was also discussed the relationship between the microstructure and tribology performances of materials. The results showed that the sliding wear resistance of material was different with its fretting wear resistance. Fretting wear resistance increased orderly: PTFE < UHMWPE < PHBA < PI < PEEK < Phenolic.

•CFs greatly improve the wear resistance of polyimide at various temperatures.•CF/PI composites display extremely low friction coefficient at high temperatures.•CFs are graphitized due to high bulk temperature, friction heat and force.•Graphitized CFs favor to the formation of self-lubricating friction films.•The lubricity of CFs strongly depends on sliding temperature.The friction and wear behaviors of neat PI and carbon fibers reinforced polyimide (CF/PI) composites were investigated at various temperatures. The results showed that the introduction of carbon fibers could greatly improve the wear resistance in the whole temperature range, while the friction coefficients strongly depended on sliding temperatures. The lubricity of carbon fibers was only found occurring at high temperatures of 180–260 °C, which can be attributed to the graphitization of carbon fibers that promotes the generation of friction and transfer films with excellent lubricity on the worn surfaces. This study is expected to provide guidance for the application of carbon fibers both as lubricating and reinforcing additives in polymer matrix sliding at high temperatures.

•High halide ions concentration improves lubricity and smoothes tribological contact.•High halide ions concentration increases corrosion tendency and corrosion rate.•High halide ions concentration is conducive to reduce material loss.Recently, increasing efforts have been made to study the tribocorrosion mechanism and influencing factors, and yet little relevant to the influence of electrolyte characteristics. In this work, the dependence of tribocorrosion on halide ions concentration in seawater is taken into consideration, and it follows that halide can improve solution lubricity and reduce friction coefficient and wear rate remarkably. However, high halide ions concentration may increase the corrosion susceptibility of 304SS, especially pitting susceptibility. Although over the entire range of halide ions concentration corrosion and wear interact positively, high halide ions concentration is beneficial for decreasing total material loss.

The tribocorrosion behavior of 304SS in chloride-containing solutions with different pH (pH 7.2–9.2) was investigated under rubbing conditions of 50 N and 100 R min−1 using a pin-on-disc tribometer with an Al2O3 pin mounted on a vertical rotating axis. When combined with rubbing, the corrosion of 304SS was accelerated due to the formation of galvanic couples between the mechanical depassivated areas and the surrounding passivated areas. In addition, the continuous sliding-over processes also make the pitting corrosion to occur more easily due to the affinity of Cl− to metal cations near the active surface. However, OH− has better affinity than Cl−; therefore, a high pH solution mitigates the local corrosion with a wear track. It was found that high pH solution exhibits good lubricity, and both the friction coefficient and total material loss reduce evidently with increasing pH. From the calculation results and wear morphologies, we can confirm that pure mechanical and corrosion-accelerated wear, including abrasion and delamination, are among the chief reasons for material loss.

•Microstructural evolution determines the extent of synergistic effects.•Microstructural evolution influences the wear resistance of 304SS.•Increasing the martensite content will change the dominant corrosion mechanism.•Delamination and abrasive wear work together to mainly mass loss of 304SS.The influence of microstructure evolution on tribocorrosion of 304SS was investigated for the first time in artificial seawater. Strain-induced α′-martensite and twinning occurred during sliding friction at room temperature. The volume fraction of transformed martensite decreased with increasing load, making the dominant corrosion mechanism changed from α′-martensite to austenite as the dissolved anode during sliding. Meantime, the extent of transformed twinning peaked at 125 N, which controlled the wear resistance of 304SS. Quantitative calculation showed the role of microstructure evolution playing in the interplay of mechanical and electrochemical reactions, which eventually resulted in accelerated degradation of 304SS.

Corrosive wear involves chemical and mechanical mechanisms and the combination of these mechanisms often results in accelerated materials degradation. In this work, pin-on-disk friction experiments were carried out in artificial seawater to investigate the influence of applied potential on the tribocorrosion behavior of 304SS. The obtained results demonstrate that when the applied potential was below the pitting potential of passive film, corrosion and wear interacted to make the total material loss increase obviously; however, when it exceeded this pitting potential, corrosion was inhibited by the rubbing process. Study of the worn surfaces and the cross-sections indicate that depending on varying applied potential, different features of wear tracks were involved, and it was the form of mechanical and corrosion-accelerated delamination wear that determined the total mass loss of 304SS during tribocorrosion.

Four types of NiCr-Cr2O3 composite coatings doped with different mass fraction of Nd2O3 were deposited by atmospheric plasma spraying. The microstructure and phase composition of as-sprayed coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). Furthermore, their friction and wear behaviors at 20 and 600 °C under unlubricated condition were evaluated using CSM high temperature tribometer. The results showed that Nd2O3 could refine microstructure of NiCr-Cr2O3 composite coating and make Cr2O3 distribution more uniform in the coating, which leads to the increase of average microhardness. In addition, NiCr-Cr2O3 composite coatings doped with Nd2O3 had better wear resistance than that without Nd2O3 at experimental temperatures. Especially, the coating containing 8 wt.% Nd2O3 showed the best wear resistance at 20 and 600 °C, which was attributed to the refined microstructure and improved microhardness. At 20 °C, the wear mechanism of the coating was abrasive wear, brittle fracture and splat detachment. At 600 °C, the wear mechanism was adhesion wear and plastic deformation.

An adaptive NiMoAl–Ag composite coating was deposited by high-velocity oxy fuel spraying, and its tribological properties from 20 to 800 °C under unlubricated conditions were evaluated using a CSM high-temperature tribometer. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were used to characterize the coating and corresponding wear tracks to determine the lubrication mechanisms. The results showed that the friction coefficient of the NiMoAl–Ag composite coating was around 0.3 from 20 to 600 °C and reached the lowest value of 0.09 at 800 °C. Meanwhile, wear rates of the coating were maintained on the order of 10−5 mm3/N m at the test temperatures except for 400 and 600 °C. Characterization of the NiMoAl–Ag coating revealed that silver provided lubrication below 400 °C. Ag2Mo2O7 and Ag2MoO4, which were formed through tribochemical reactions, acted as high-temperature lubricants above 400 °C. It was especially proposed that silver in a nearly molten state was effective in reducing the friction of the NiMoAl–Ag coating at 800 °C. Moreover, a comprehensive lubrication mechanism model of an NiMoAl–Ag composite coating at 800 °C was established to explain the extremely low friction coefficient and wear rate of the coating.

The tribological behaviors of ultra-high molecular weight polyethylene (UHMWPE) microparticle-modified high-strength glass fabric/phenolic laminate composites sliding against stainless steel under water lubrication have been investigated. Results showed that the incorporation of UHMWPE microparticles, especially at the mass fraction of 5.0 %, improved the wear resistance of the laminate composite to a significant extent, because UHMWPE microparticle can effectively absorb and dissipate the friction energy through a plastic deformation during the formation of the regular ripple-like abrasion patterns on its worn surface. During the sliding process, after the phenolic resin was firstly worn off, UHMWPE microparticles with much better wear resistance were protruded from the worn surface of the laminate composite, leading to a fundamental change in the contact status of the matched surfaces from rigid resin and fibers/steel to flexible UHMWPE/steel. As a result, low and steady friction coefficient was obtained due to good adaptability of UHMWPE to water lubrication.

•Treatment on fillers greatly enhanced interfacial bond in laminate.•Treatment on fillers improved ILSS and tribological properties of the laminate.•Combined treatments were more effective than the single treatment.•Treatment on fillers improved the duration of the laminate in water environment.The ternary laminate composite of ultra high molecular weight polyethylene (UHMWPE)/high strength glass fabric (S-glass fabric)/phenolic resin was prepared, in which UHMWPE microparticles were etched by chromic acid and S-glass fabrics were treated by silane coupling agent. The interlaminar shear strength (ILSS) and tribological properties of the composite in water environment were investigated, in comparison with those of the composite without any treatments on fillers and the composite with single treatment on UHMWPE. Results showed that the composite with the combined treatment exhibited the best interfacial bond, accordingly showing remarkably enhanced water repellency, ILSS and tribological properties under water lubrication. Furthermore, after experiencing 48 h water immersion, the composites with both single and combined treatment did not suffer any degradation of ILSS and water-lubricated tribological performances, showing excellent duration in water environment.

Tribological behaviors of Si3N4 ceramic sliding against 316 stainless steel under seawater lubrication were investigated and compared with those under dry sliding and pure water lubrication. The results showed that SiO2 colloidal particles were formed on the rubbing surface of Si3N4 due to the friction-induced chemical reaction of Si3N4 with H2O, which were further aggregated into the silica gel with the assistance of ions in seawater. Because of the boundary lubrication of the silica gel layer, both the lowest friction coefficient and the smallest wear rates of Si3N4 and 316 steel were obtained in seawater.Highlights► Excellent lubrication was obtained for Si3N4/316SS in seawater. ► The wear rates of the both Si3N4 and 316SS were the lowest in seawater. ► The tribochemical reaction of Si3N4 and H2O forms the colloidal silica in water. ► The colloidal silica can be aggregated into silica gel in seawater. ► The excellent lubrication in seawater is attributed to the deposited silica gel.

•Adaptive NiCrAlY–Ag–Mo composite coating was firstly produced by atmospheric plasma spraying technology.•The composite coating exhibited show good cohesive strength and low porosity.•The composite coating shows stable and low friction coefficients around 0.3 from 20 °C to 800 °C.Adaptive NiCrAlY–Ag–Mo composite coating was deposited by atmospheric plasma spraying and its tribological properties from 20 °C to 800 °C under unlubricated conditions were evaluated using CSM high temperature tribometer. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the coating and the corresponding wear tracks to determine the lubrication mechanisms. The results showed that NiCrAlY–Ag–Mo composite coating exhibited low friction coefficients around 0.3 in the entire temperature range and its wear rates were at the order of 10− 5 mm3/N m at all test temperatures. Characterization of NiCrAlY–Ag–Mo coating revealed that silver provided lubrication at temperatures below 400 °C. Silver molybdate and molybdenum oxide, which were formed as the temperature raised, act as lubricants at higher temperature (above 400 °C). Meanwhile, the formation mechanism of silver molybdate and molybdenum oxide was also briefly discussed.