As the use of marine systems grows and the requirements for seawater lubrication grows, the performance of key marine alloys used in propulsion, bearings and mechanical seals is under scrutiny. For ...example, the increased use and size of bulk carriers and ocean liners requires performance of propellers to be better understood and cavitation resistance needs to be predicted and improved. The growth in marine autonomous and renewable energy systems as well as aquaculture also places emphasise on greater understanding of marine alloy tribocorrosion performance. Therefore, this paper will review marine wear and tribocorrosion and focus on candidate or existing materials for the components must at risk of wear (i.e. propulsion and seawater handling systems) and the mitigating strategies used to limit effects of wear in aggressive ocean environments. It will look at recent research into the performance of cast nickel aluminium bronze, a propulsion material of choice, under cavitation erosion and sliding wear conditions in saline solutions. The mass loss and in-situ electrochemical measurements during cavitation erosion corrosion over time will be presented along with detailed reference to microstructural and compositional changes on the surface and subsurface. The influence of surface films and their stability will be explored. For sliding wear tests the temporal aspects of film removal and repair as a function of sliding frequency will be presented along with complimentary wear rates, friction and corrosion currents. Some initial results on coatings and bulk composite alternatives to NAB will also be presented. Research into solid particle erosion-corrosion will also be presented for NAB. The challenges in quantification of the interactions between mechanical and electrochemical processes present under marine tribocorrosion are discussed in detail.
•presents performance of selected marine alloys under different tribocorrosion conditions.•results reveal different synergistic levels dependent on test conditions and pre-immersion.•The difficulties in quantification in synergy levels is explored.•New data on marine composites resistance to cavitation erosion is presented.
Auxetics are a modern class of material fabricated by altering the material microstructure. Unlike conventional materials, auxetics exhibit a negative Poisson's ratio when subjected to tensile ...loading. These materials have gained popularity within the research community because of their enhanced properties, such as density, stiffness, fracture toughness and dampening. This paper provides a critical oversight of the auxetic field with particular emphasis to the auxetic foams, due to their low price, easy availability and desirable mechanical properties. Key areas discussed include the fabrication method, the effects played by different parameters (temperature, heating time, cell shape and size and volumetric compression ratio), microstructural models, mechanical properties and potential applications.
In this Feature Article, Critchley et al. introduce the expanding field of auxetic materials and critically review the literature with a primary focus on auxetic foams. Particular attention is given to the fabrication methodologies, the influence played by the fabrication parameters, the microstructural models (both two‐ and three‐dimensional), the mechanical properties and the potential applications of these materials.
Surface textures have been of great interest within the tribology community with nearly 1500 papers published on this topic in the past two decades. With the pursuit of low emissions and ...environmental sustainability, the application of surface texturing to mechanical systems to lower friction and control wear is attracting increasing attention. There is no doubt that certain textured surfaces can have a beneficial effect on tribological performance but it is widely agreed that the optimization of textures should be carried out based on specific requirements of applications. The purpose of this review article is to summarize the current state of the art in surface texturing applied to mechanical applications (cutting tools, piston-ring & cylinder liners, sealing and journal bearings) from the following aspects: application requirements, numerical/experimental testing and validation, and tribological performance of textured surfaces (wear and friction), as well as the limitations in texture designs when applied to certain applications. Patterns/grooves in the micron-scale are the most typical shapes been studied, and benefits of partial texturing are applicable for most of these mechanical applications. Friction reduction of up to 34.5% in cutting tools, 82% in piston-ring & cylinder-liners, 65% in seals and 18% in journal bearings have been observed by experimental tests. Based on primary evidence from the literature, the last section provides general suggestions on current gaps in understanding and modelling and suggestions for future research directions.
Tribo-corrosion of coatings: a review Wood, Robert J K
Journal of physics. D, Applied physics,
09/2007, Letnik:
40, Številka:
18
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
This paper reviews the available literature relating to the emerging research into the performance of coatings under combined wear and corrosion conditions. Understanding how coatings perform under ...these tribo-corrosion conditions is essential if the service life of equipment is to be predicted and to allow service life to be extended. Therefore, the tribo-corrosion performance of coatings deposited by a variety of techniques is discussed and the main mechanisms associated with their degradation under combined wear and corrosion highlighted. Coating composition, microstructure, defect level, adhesion, cohesion and substrate properties are seen as some of the critical elements in coating performance when subjected to tribo-corrosion contacts. The importance of post-coating deposition treatments such as laser resurfacing and sealing are also discussed. Interactions between wear and corrosion mechanisms are identified along with some models and mapping techniques that aim to inform coating selection and predict performance. Recent investigations into mono-layer as well as multilayered and functionally graded coatings are reviewed as candidates for wear-corrosion resistant surfaces. The review reveals the need for a more considered approach to tribo-corrosion testing and the way in which the results are analysed and presented. For example, the test conditions should be appropriate to the coating system under test; the level of in situ instrumentation deployed and the post-test analysis of in situ electrochemical data should be carefully selected as well as details given of the composition of any surface tribofilms formed and the identification of the degradation mechanisms.
To explore anti-wear characteristics for valve pair, the influences of smooth and non-smooth surfaces on tribological properties of the carbon-fiber-reinforced polyetheretherketone (CFRPEEK) coupled ...with stainless steel 316L were investigated under natural seawater lubrication. The results show that the specimen with ellipsoidal pits has the best frictional performance, followed by the specimen with triangular pits, and the specimen with hemispherical pits is the worst. Microscope observation analysis showed that the reasonable non-smooth surface can reduce adhesion wear and improved the stability of friction system as compared to smooth surface. Results also indicated that the reasonable non-smooth unit can effectively store seawater and debris, and produce hydrodynamic lubrication effect, which surface shows the excellent tribological properties.
In this paper, to explore the tribological characteristics of the end-face valve pair of seawater hydraulic motor, different types of bionic non-smooth macro units were processed on the surface of CFR/PEEK specimens using CNC machine tool and the friction pair was formed after coupling with another surface of 316L stainless steel. To study the friction and wear properties of bionic non-smooth surfaces with different morphologies under seawater lubrication, the relative rotating process of valve pairs in seawater was simulated by MMD-5A end-face wear tester, and the three-dimensional topography and roughness of all specimens before and after the experiment were observed by optical three-dimensional surface measuring instrument. Finally, some results were obtained and discussed.Fig.1. Schematic diagram of MMD-5A friction and wear tester and installation drawing of ring-on-disc tester. Display omitted
•The effect of surface texture with different shapes and geometries on tribological characteristics under seawater lubrication was analyzed.•The friction and wear properties of bionic non-smooth surfaces with different morphologies were investigated.•The three-dimensional topography and roughness of all samples were observed by surface measuring instrument.•The specimen with ellipsoidal pits has the lowest friction coefficient and the best anti-wear effect.
Processing by severe plastic deformation (SPD) has been developed extensively over the last two decades in order to produce ultrafine-grained (UFG) materials having submicrometre or nanometre grain ...sizes. An important material property for UFG materials is good wear resistance so that they may be used in a range of structural applications. An examination of the published data shows that only limited reports are available to date on the wear behaviour of SPD-processed materials and, furthermore, many of these results appear to be conflicting. The correlation of hardness and wear is limited because the wear property is a system property that in practice is influenced by a range of factors. Accordingly, this review is designed to examine recent reports related to the wear resistance of materials processed by SPD with particular emphasis on alloys processed using equal-channel angular pressing (ECAP), high-pressure torsion (HPT) and accumulative roll-bonding (ARB).
Cemented and thermal sprayed tungsten carbide are extensively used in a wide range of applications, ranging from downhole drilling tools and oil and gas valves to gas turbine engines. These WC based ...systems offer improved wear resistance as a result of hard ceramic phases surrounded by a metallic binder matrix. However, the presence of hard and soft phases within these materials also leads to differing wear mechanisms and the formation of micro-galvanic couplings in aqueous environments often result in a reduction in combined wear-corrosion resistance. This paper examines the wear-corrosion performance of these WC based systems in a range of wear, electrochemical and wear-corrosion tests to develop models and establish relationships between wear mechanisms and environmental factors such as pH.
•Significant difference in composition and structure between cemented WC and WC coating.•Tribocorrosion is an area of significant interest and needs further understanding.•Understanding of individual degradation mechanisms is required.•Numerical modelling provides a method for understanding and prediction of degradation.
Running-in occurs in rolling-sliding contacts under mixed-friction conditions and typically involves asperity smoothing through mild wear and plastic deformation. To improve the prediction of service ...life or friction of rolling-element bearings under mixed-friction conditions, knowledge of surface topography changes during running-in and their dependence on the operating condition is an important prerequisite. Therefore, this study aims to describe the surface mechanisms due to wear, during running-in and their dependence on one of the variables, slip.
AISI 52100 steel specimens were tested in a mini traction machine (MTM) instrumented with friction and contact potential measurement in the presence of a PAO base oil, operating in the mixed lubrication regime. A novel method of pre and post-test surface relocation with 3-D optical profilometry and scanning electron microscopy (SEM) was implemented. Rolling-sliding tests were performed to study the effect of slide-roll ratio on the surface topography changes during running-in. Additional tests were conducted to track the changes to surface topography during this period.
The results exhibit the rapid nature of running-in and how most of the surface topography changes occur in the first few load cycles. Surface topography transitions such as asperity removal due to wear, increase in the load-bearing area of the asperities and in tests with slip, plastic flow of material from peaks into adjacent valleys are shown at high magnification. Surface profilometry measurements show that the reduction in depth of the valleys due to plastic flow adds to the reduction in roughness, thus accurately identifying the surface mechanism, and redressing the consensus that the reduction in roughness during running-in is mainly due to wear and plastic deformation diminishing the height of the peaks, which is true for ideal running-in alone.
•During running-in asperity peaks undergo wear and plastic deformation.•Slip is an aggressor of plastic deformation during running-in and results in asperity level material flow.
A top DLC film was deposited on the surface of Cr3C2-NiCr coated 38CrMoAl steel substrate, and the effect of Cr3C2-NiCr cermet interlayer thickness on the mechanical and tribological properties of ...the duplex coating was investigated by experimental analysis and finite element modeling (FEM). Results shown that, compared with single DLC film, the load-bearing capacity and tribological performance of DLC/Cr3C2-NiCr duplex coating were significantly improved, especially its anti-wear performance was nearly ten times higher than that of the single DLC film. Moreover, the duplex coating with an optimum cermet interlayer thickness of 100 μm showed the best comprehensive performance. FEM analysis also shown that the presence of Cr3C2-NiCr cermet interlayer limited the stress concentration area within the interlayer, which made the stress concentration area far away from the interface of DLC film and cermet interlayer, thus improved duplex coating durability. What's more, the cermet interlayer thickness increase resulted in the contact stress on DLC film increase, which contributed to the improvement of its tribological performance.
•C100 duplex coating achieved superior mechanical and tribological properties.•C100 duplex coating anti-wear rate is ten times higher than single DLC film.•Stress concentration in C100 is the farthest against film/cermet interlayer interface.•Thickened interlayer increased contact stress and intensified DLC graphitization.
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