Jianzhang Wang

Synergetic Effect of Lubricant Additive and Reinforcement Additive on the Tribological Behaviors of PEEK-Based Composites under Seawater Lubrication

Polyetheretherketone (PEEK)-based composites reinforced with lubricant additive (polytetrafluoroethylene, PTFE) and reinforcement additives including carbon fiber (CF), glass fiber (GF), and bronze powder were prepared using a hot-press molding technique. The synergetic effects of different additives on the tribological behaviors of PEEK-based composites sliding against 316 steel under seawater lubrication were investigated systematically using a ring-on-block test rig. The results showed that lubricant additive PTFE can decrease the friction coefficient and consequently improved the wear resistance of PEEK under seawater lubrication, especially when the volume fraction of PTFE was about 20%. It was also found that the incorporation of CF can further improve the wear resistance of PEEK blended with 20% PTFE, especially under high load and high sliding speed. This suggested that a synergistic effect on improving the wear resistance of PEEK existed between PTFE and CF, which originated from good lubrication of PTFE, good reinforcement of CF, and good interfacial combination between CF and PEEK-20%PTFE. However, two other reinforcement additives of GF and bronze powder had an antagonistic effect but not a synergetic effect with PTFE; that is, the incorporation of the two additives greatly deteriorated the wear resistance of PEEK blended with 20% PTFE.

Microstructure of PTFE-Based Polymer Blends and Their Tribological Behaviors Under Aqueous Environment

Four polytetrafluoroethylene-based polymer blends (PTFE blends) with polyimide (PI), polyether ether ketone (PEEK), poly(phenyl p-hydroxybenzoate) (PHBA), and perfluoroethylene propylene copolymer (FEP) were prepared by compression molding and follow-up sintering. Their microstructure was observed by scanning electron microscope. And the tribological behaviors of PTFE blends sliding against 316 steel under pure water and sea water lubrication were comparatively evaluated using block-on-ring tribology test rig. The worn surface of counterpart was examined by X-ray photoelectron spectroscopy. The results showed that by blending with the four polymers, PTFE exhibited the transformed microstructure and improved wear resistance. Compared with FEP, rigid polymers PI, PHBA, and PEEK can enhance the wear resistance of PTFE greatly because they can effectively improve the load-carrying capacity of PTFE matrix and can more efficiently prevent the crystalline bands of PTFE from being pulled out. However, because of the weak inhibition on the pulling out of PTFE crystalline bands, FEP cannot enhance the wear resistance of PTFE as significantly as other polymers. In addition, the friction coefficients and wear rates of PTFE and its blends were lower under the lubrication of sea water than under the lubrication of pure water, which was ascribed to more excellent lubricating effect of sea water originating from the deposition of CaCO3 and Mg(OH)2 onto the sliding surfaces.

Comparative Investigation on the Friction and Wear Behaviors of Carbon Fabric–Reinforced Phenolic Composites under Seawater Lubrication

Carbon fabric–reinforced phenolic composites were prepared by dip-coating and hot press-molding techniques. The interlaminar shear strength (ILSS) of phenolic composites was determined by a three-point bending test on a universal material testing machine and their friction and wear behaviors under dry friction, pure water, and seawater lubrication were investigated comparatively using a block-on-ring test rig. Experimental results showed that carbon fabric–reinforced phenolic composite with 30 wt% resin had the best ILSS and tribological properties, and the ILSS of phenolic composites decreased with increasing content of resin. When experiencing immersion in pure water and seawater for 24 h, the ILSS of phenolic composites decreased greatly, and this decrease was in particular more obvious after immersion in pure water. In addition, compared to dry sliding condition, phenolic composites exhibited much better tribological properties under seawater lubrication but worse tribological properties under pure water lubrication. The differences in the tribological behaviors of phenolic composites were determined by two competitive effects of aqueous medium, including cooling, lubricating and washing effect, and plasticization effect. Moreover, the wear mechanisms of phenolic composites under dry friction and lubrication with aqueous media were adhesive wear and slight abrasive wear, respectively.

Comparison of tribocorrosion behavior between 304 austenitic and 410 martensitic stainless steels in artificial seawater

In order to obtain a comprehensive understanding of the tribocorrosion performance of 304 austenitic and 410 martensitic stainless steels in artificial seawater, systematic tests were carried out in this work. The results from intermittent test revealed that load and sliding speed had great influence on the cathodic shift of OCP caused by sliding wear. Through potentiodynamic and potentiostatic polarization tests, which were performed under cathodic, OCP and anodic potentials, it was confirmed that synergistic effects existed between wear and corrosion and were linked with applied potential. In addition, it was found that tribocorrosion behavior of the two alloys was affected by microstructural characteristics and chemical composition, which were closely related to the mechanical properties and repassivation kinetics of passive film. Particularly, 304SS exhibited a better localized corrosion resistance compared with that of 410SS due to the higher content of chromium and nickel. For both materials, hardness inside the wear track was higher compared with the unworn surface due to a rubbing-induced hardening effect.

Corrosion wear synergistic behavior of Hastelloy C276 alloy in artificial seawater

Abstract A systematic investigation was carried out to discuss the corrosion and tribocorrosion behaviors of Hastelloy C276 alloy sliding against Al 2 O 3 pin in artificial seawater, using a pin-on-disk tribometer integrated with a potentiostat for electrochemical control. The results show that the great decrease of open circuit potential and three orders of magnitude increase of corrosion current density occur caused by friction. There are clearly synergistic effect between corrosion and wear, resulting in corrosion-induced-wear and wear-induced-corrosion in tribocorrosion process. The contribution of pure mechanical wear to total material loss exceeds 70% in all sliding conditions, so mechanical wear is the dominant factor during tribocorrosion. For considering synergistic effect between corrosion and wear, the contribution of wear-induced-corrosion to total material loss is not very high although corrosion rate is greatly accelerated by friction. The fraction of corrosion-induced-wear to the total material loss is high and in the range of 14.6%–20.5% under all sliding conditions.

Combined Effect of Chemical Surface Treatment of Kevlar Fabric and PTFE Fillers on the Water-Involved Tribological Performance of Kevlar Fabric/Phenolic Laminate

ABSTRACT The combined effect of chemical surface treatment of Kevlar fabric and solid lubricant polytetrafluoroethylene (PTFE) fillers on the water-involved tribological performance of Kevlar fabric/phenolic resin laminate was investigated. Results showed that the interfacial adhesion between Kevlar fabric and resin was improved because of chemical surface treatment on the Kevlar fabric, leading to a decreased wear rate but an increased friction coefficient of the laminate. The addition of PTFE fillers not only enhanced the wear resistance of the laminate but reduced its friction coefficient. Furthermore, the combination of surface treatment on Kevlar fabric and the PTFE filling can improve the wear resistance and friction-reducing property of the laminate to the largest extent.

Synergism of Poly(p-phenylene benzobisoxazole) Microfibers and Carbon Nanofibers on Improving the Wear Resistance of Polyimide–Matrix Composites in Sea Water

Polyimide (PI)–matrix composites reinforced by poly(p-phenylene benzobisoxazole) (PBO) microfibers and carbon nanofibers were prepared, and wear behaviors of the composites sliding against stainless steel in sea water were investigated. The results showed that the single incorporation of PBO microfibers or carbon nanofibers can significantly improve the wear resistance of PI–matrix composites. Further, a synergistic effect between PBO microfibers and carbon nanofibers was found. Namely, hybrid incorporation of the two fibers led to the best wear resistance of PI–matrix composites. During the friction and wear process, flexible PBO microfibers can effectively absorb and dissipate the friction energy; stiff carbon nanofibers can protect the PBO/PI interfaces and the PBO microfibers from mechanical damage.

Effects of NaCl concentration on wear–corrosion behavior of SAF 2507 super duplex stainless steel

Wear–corrosion behavior of SAF 2507 super duplex stainless steel (SDSS) in different concentrations of NaCl (from 0.5% to 8%, w/v) was investigated using a pin-on-disk tester. Friction coefficient and mass loss rate were determined, and the synergistic effect of wear and corrosion was analyzed by tribocorrosion-related parameters. It was indicated that wear–corrosion regimes were significantly influenced by NaCl concentration and the related mechanism was attributed to the two different phases inside SAF 2507. Self-protection behavior between the two phases inside SAF 2507 led to a significantly different wear–corrosion mechanism, compared to that in the single-phase metal. To the best of our knowledge, this is the first study about wear–corrosion behavior of SAF 5207 within a solution with different corrosivity. This research provided a new insight for researchers to look into the tribocorrosion behavior of alloys with different phases, and helped us to better understand the principle that we should follow while developing alloys employed in a corrosive environment.

Accelerated degradation of polyetheretherketone and its composites in the deep sea

The performance of polymer composites in seawater, under high hydrostatic pressure (typically few tens of MPa), for simulating exposures at great depths in seas and oceans, has been little studied. In this paper, polyetheretherketone (PEEK) and its composites reinforced by carbon fibres and glass fibres were prepared. The seawater environment with different seawater hydrostatic pressure ranging from normal pressure to 40 MPa was simulated with special equipment, in which the seawater absorption and wear behaviour of PEEK and PEEK-based composites were examined in situ. The effects of seawater hydrostatic pressure on the mechanical properties, wear resistance and microstructure of PEEK and its composites were focused on. The results showed that seawater absorption of PEEK and its composites were greatly accelerated by increased hydrostatic pressure in the deep sea. Affected by seawater absorption, both for neat PEEK and composites, the degradation on mechanical properties, wear resistance and crystallinity were induced, the degree of which was increasingly serious with the increase of hydrostatic pressure of seawater environment. There existed a good correlation in an identical form of exponential function between the wear rate and the seawater hydrostatic pressure. Moreover, the corresponding mechanisms of the effects of deep-sea hydrostatic pressure were also discussed.

Corrosion-wear behavior of 316L stainless steel under different applied potentials

Purpose This report aims to study the influence of applied potentials on the corrosion-wear behavior of 316L stainless steel (SS) in artificial seawater. Design/methodology/approach 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. Findings 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. Practical implications The results helped us to choose the appropriate metals for application under the specified environment. Originality/value 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.