•Tribocorrosion mechanisms of DLC coating in seawater were systematical investigated.•The corrosion-induced wear occupied a dominant position for 304L substrate.•The mainly volume loss of DLC coating in seawater was due to mechanical wear.•The COF of DLC coating keeps stable and wear loss increases as potential increased.The multilayer DLC coating was successfully fabricated on the surface of 304L stainless steel and silicon wafers by unbalanced magnetron sputtering technology. The tribocorrosion tests were carried out in a triboelectrochemical cell using a ball-on-plate tribometer integrated with a potentiostat for electrochemical control. Results showed that the open circuit potential (OCP) and corrosion potential (Ecorr) of 304L substrate presented great fluctuation. However, the OCP and Ecorr values of the multilayer DLC coating remained relatively stable during these tests. Meanwhile, the friction coefficient decreased and the wear-loss increased with the polarization potential increased from − 1 to 0.5 V. In addition, with an increase in polarization potential, the mechanical wear decreased obviously and the corrosion-induced wear gradually occupied a dominant position for 304L substrate, nevertheless, the mainly volume loss of the multilayer DLC coating was mainly attributed to pure mechanical wear. Thus, the tribocorrosion resistance of the multilayer DLC coating was superior to 304L substrate in seawater, manifesting its good potential as a protective material for marine industry.Download high-res image (175KB)Download full-size image

•Typical DLC, GLC and CrN coatings were fabricated by PVD technology.•Load carrying capacities of coatings in different conditions were investigated.•Thicker CrN with good mechanical behavior exhibits high load carrying capacities.•The GLC coating possessed the best load carrying capacity in distilled water.DLC, GLC and CrN coatings of different thicknesses were prepared by PVD technology using their respective mature process parameters. Field emission scanning electron microscope (FESEM), laser confocal microscopy, and Raman spectrometer were used to analyze the morphologies and microstructures of the coatings. Nanoindentation measurements and scratch tests were executed to characterize mechanical properties. The load carrying capacities of these coatings in ambient air, distilled water and oil environments were investigated by a reciprocating tribometer with gradually increasing applied load. Results show that the CrN(2 h) coating has the best load carrying capacity in ambient air and base oil, the GLC coating possesses the best load carrying capacity in distilled water. The DLC coating exhibits lower friction when it survives under low load. The different load carrying capacities of these coatings under sliding-friction condition are closely related to their surface roughness, coating thickness and mechanical properties.

•The Si contents are significantly affect the structure of CrAlSiN coatings.•The Cr2O3,CrN,AlN and Si3N4 phases were formed in CrAlSiN coatings.•Tribological tests were carried out on CrAlSiN coatings in artificial seawater.•The CrAlSiN coating (5.5 at.%) exhibited the lowest wear loss among them.Nanocomposite CrAlSiN coatings with different Si percentages were deposited using a multi-arc ion plating technique. The coating microstructures were characterized by SEM, XRD, XPS and TEM. The mechanical properties and tribological performances were measured. The results demonstrated that the microstructure of the CrAlSiN coatings was composed of (Cr, Al) N crystallites and an amorphous Si3N4 phase. With increasing Si content, the thickness of the as-deposited coating increased gradually, and the hardness, toughness and adhesion force first increased and then decreased. The CrAlSiN coating containing 5.5 at.% Si exhibited the optimal tribological properties in seawater. The significant improvement in the tribological performances is closely related to the formation of self-lubricating SiO2 and the enhancement of comprehensive properties.

•The nc-CrC/GLC film is successfully achieved by magnetron sputtering system.•The tribological behaviors were affected by the mechanical properties of tribopair.•The tribo-chemical products on interface have obviously effect on friction behavior.•The COF and wear rate of nc-CrC/GLC film sliding against Al was lower than others.•The wear mechanism of nc-CrC/GLC film sliding against different metals is explained.In order to discuss the wear situation of nc-CrC/GLC film sliding against different counterparts in seawater, the nc-CrC/GLC film was fabricated by unbalance magnetron sputtering technique on silicon wafer and 304L stainless steel. The SEM, Raman, TEM were used to measure the morphologies, components and microstructures of nc-CrC/GLC film. The nanoindentation test was used to acquire the hardness and elastic modulus of nc-CrC/GLC film. The tribological performances of nc-CrC/GLC film sliding against different metallic counterparts including Al, Ti, H62, GCr15 in seawater were comparatively investigated by a reciprocating tribo-meter and the tribological mechanisms were highly analyzed via Hertz contact theory. The tribo-chemical products, worn surfaces of nc-CrC/GLC film and metallic counterpart were observed by scanning electron microscope (SEM). The results showed that the hardness and elastic modulus of nc-CrC/GLC film were about 14.09 ± 1.32 and 169.16 ± 13.39 GPa, respectively The friction coefficients of nc-CrC/GLC film sliding against H62, GCr15, Ti, Al counterparts were about 0.18, 0.135, 0.085 and 0.06, respectively. Meanwhile, it was found that the wear rate of nc-CrC/GLC-Al was the lowest value of 0.23 × 10− 7 mm3/Nm, while the wear rate of nc-CrC/GLC-H62 was the highest value of 1.79 × 10− 7 mm3/Nm. The tribological performances of nc-CrC/GLC film would be improved by chosen an appropriate counterpart. The nc-CrC/GLC-Al showed low friction and wear in mixed lubrication, and the wear mechanism was regarded as adhesive and corrosion wear. Whereas the nc-CrC/GLC-Ti and nc-CrC/GLC-GCr15 were known as corrosion and three-body abrasive wear, the nc-CrC/GLC-H62 showed a hybrid mechanism of adhesive, abrasive and corrosion wear.Download high-res image (239KB)Download full-size image

The tribological performances of the graphite-like carbon (GLC) films sliding against WC balls in distilled water (DW), artificial seawater (SW) and four types of saline solutions related to seawater were investigated. The GLC film was deposited by magnetron sputtering. The microstructure, mechanical properties and tribological performances of the GLC film were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, nano-indentation and reciprocating ball-on-disk tribo-meter. The results showed that the smooth, dense and hard GLC film with significant sp2-hybridized carbon exhibited good tribological performance with low friction and wear not only in distilled water, but also in seawater. The tribological performance of the GLC film in seawater was closely related to the nature and constitution of seawater, as well as the nature and performance of the counterparts. Bulky wear debris with hard particles would generate a three-body wear regime, which increases the friction coefficient and wear rate of the GLC film slightly in seawater environment. In contrast, the divalent metal salts of seawater can decrease friction and wear between the two contact surfaces. The synergistic effect led to a relatively higher friction coefficient and wear rate of the GLC film against the WC counterpart in seawater than that in distilled water.

•Cr/GLC film presented excellent anti-corrosion performances in variable pH solutions.•The tribological behavior of Cr/GLC film and Si3N4 tribopair is highly pH-dependence.•Tribochemical layer contributed to good tribological performances in acid solutions.•Low friction in alkaline solutions may be ascribed to double electric layer.The corrosive behaviors and tribological performances were investigated for chromium doped graphite-like carbon films in variable pH solutions. Results showed that the as-deposited films could present good corrosion resistances in aggressive solutions that might be attributed to the effect of chromium and chromic oxide. Also, it could exhibit a great pH-dependence for the tribological behaviors of films when sliding against Si3N4 balls in aggressive solutions. The tribo-chemical reactions should play significant roles in superior tribological performances for as-deposited films in aggressive solutions. However, the poor wettability could result in a high friction coefficient for tribopair in pH=14 solution.

•Cr7C3 strengthening phase was found after the Cr doping to the GLC film.•Cr/GLC film coupling with different ceramics exhibited different friction behaviors.•The tribological behaviors were affected by the mechanical properties of tribopair.•The tribo-chemical products on interface have obviously effect on friction behavior.•The COF and wear rate of Cr/GLC film sliding against Si3N4 was lower than others.The tribological performances of Cr/GLC film coupling with Si3N4, SiC, WC, Al2O3 and ZrO2 were comparatively studied in seawater. Results indicated that the Cr/GLC film coupling with different ceramic counterparts exhibited different friction behaviors, which was closely related to the mechanical performances of mating ceramics. Meanwhile, the tribo-chemical products between the Cr/GLC film and ceramics also played an important role in improving the tribological performances. Friction coefficient and wear rate of the Cr/GLC film sliding against Si3N4 were lower than others, which indicated that the Cr/GLC film coupled to Si3N4 ceramic exhibited optimum tribological performance in seawater.

To improve the tribological performance of 316L in seawater, the CrN and CrSiN coatings were deposited by multi-arc ion plating. The coatings were systematically characterized. Corrosion properties were evaluated by immersion test and anodic polarization measurement. The friction and wear properties of the CrN and CrSiN coatings were investigated by ball-on-disk tribometer in artificial seawater. The results show that the CrN coating has strong (111) and (200) preferred orientations and the intensity of the peaks decreases for the CrSiN coating. The hardness of the CrSiN coating is higher than that of the CrN coating. The CrSiN coating presents better corrosion resistance in seawater. The friction coefficient and wear rate of the CrSiN coating are lower than those of the CrN coating, indicating positive effect of Si addition on tribological performance in seawater. The coatings could significantly improve the wear resistance of the 316L in seawater.

•Sliding contact had a significant effect on the OCP and Ecorr for 316L.•The OCP for the CrN coating remained relatively stable during the sliding.•The friction coefficient decreases and wear volume increases as potential increased.•The corrosion-accelerated wear contribution increases with increase of potential.The tribocorrosion behavior of type 316L stainless steel and CrN coated 316L by PVD was investigated in seawater environment. Tests were carried out in a triboelectrochemical cell using a ball-on-plate tribometer integrated with a potentiostat for electrochemical control. Sliding contact against silicon nitride balls had a significant effect on the open circuit potential (OCP) and corrosion potential (Ecorr) for 316L. However, the OCP for the CrN coating remained relatively stable during the sliding. Tribocorrosion tests performed under various applied potentials demonstrated that the friction coefficient decreased and wear-loss increased as the applied potential increased from −1 V to 0 V. Under cathodic potential of −1 V, abrasive wear form of mechanical wear dominated the wear of 316L stainless steel. As the potential increases, the general corrosion was observed and tribo-corrosive contributions to the wear increased. Plastic deformation dominated the wear process of CrN coating under a cathodic potential. With an increase in potential, the mechanical wear contribution decreased and corrosion-accelerated wear contribution increased. At high anodic potential (0.5 V), pitting corrosion occurred in the wear track and on the outer part of wear track on 316L and CrN coated 316L.

•Carbon content plays an important role in structure and properties of CrCN coatings.•The carbon exists as sp2C–C/C–N, sp3C–C/C–N and Cr–C bonds in CrCN coatings.•Nanocystallites/amorphous matrix structure is observed in CrCN coating.•(200) plans are symmetrically distributed and form the twinning structure.•The CrCN coating (10–15 sccm) exhibited the lowest wear loss among them.CrCN coatings were deposited using the multi-arc ion plating with different C2H2 flow rates. Microstructures, mechanical and tribological performances were systematically investigated. The results showed that the peak intensity correlated to Cr7C3 crystal phase became stronger when the flow rates increased from 0 to 15 sccm, whereas, it was decreased when the C2H2 flow rate increased to 30 sccm. The hardness increased to 32.5 GPa due to formation of Cr7C3 phase and amorphous CNx at 10 sccm. CrCN coatings deposited at 10–15 sccm exhibited a better comprehensive performance, indicating their potential application as a protective coating for tribo-components in seawater.

•Tribological tests were carried out on PVD CrN coatings in seawater.•The multilayer coating controls wear failure effectively in seawater.•A comprehensive wear model of the CrN coatings in seawater was established.•Several feasible methods were proposed to control wear failure of CrN coatings.Four CrN coatings were deposited on 316L stainless steel by multi-arc ion plating. The tribological behaviors of the CrN coatings were investigated by ball-on-disk tribometer in seawater. The microstructure and wear track were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and profilometer. The result shows delamination is critical to wear failure of CrN coatings in seawater and micro-cracks play an important role in the evolution of delamination. The most effective approach to eliminate the delamination is fabricating a proper multilayer structure, which could limit crack propagation only to the layer. A comprehensive wear model is established.

•Microstructure and property of GLC film are dependent on deposition target power.•Decreased elastic modulus leads to the increase of friction in ambient air.•Water lubrication results in the similar low friction if the GLC film can survive.•Decrease of mechanical properties causes the increase of wear rate in ambient air.•Decrease of film compactness generates the increase of wear rate in water.Graphite-like carbon (GLC) films were deposited using magnetron sputtering technique with different target currents. With the increase of target current, the deposition rate and sp2 site increased, while the mechanical properties and film compactness decreased. In ambient air, decreased elastic modulus led to the high friction of GLC film. In distilled water, water lubrication resulted in the similar low friction coefficients if the GLC film could survive. The decrease of mechanical properties caused the increase of specific wear rate in ambient air. The decrease of film compactness generated the increase of specific wear rate in distilled water.