Reduction In Wear Volume Research Articles

Influence of Al2O3 reinforcements and Ti-Al intermetallics on corrosion and tribocorrosion behavior of titanium

Ti-Al2O3 composites have demonstrated favorable characteristics for use in load-bearing biomedical implant applications; however, the influence of Al2O3 reinforcement particles and Ti-Al intermetallics on the electrochemical and tribo-electrochemical responses of Ti are not well-understood. This study explored the corrosion and tribocorrosion characteristics of powder metallurgy-manufactured Ti-Al2O3 composites in a simple physiological saline solution at body temperature. Electrochemical analysis was performed by electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization and tribo-electrochemical mechanisms were explored under open circuit potential (OCP) against a 10 mm diameter alumina ball in a ball-on-plate tribometer with reciprocating configuration. Results revealed that the corrosion behavior of Ti was adversely affected by the development of a heterogeneous oxide film on the Ti matrix and the Ti-Al intermetallic phases formed by the interaction of Ti and Al2O3 particles. However, there was a drastic improvement in tribocorrosion behavior, evidenced by decreased corrosion tendency under sliding and a marked reduction in wear volume, primarily as a result of the decreased wear damage resulting from the load-bearing reinforcements.

A snowboard-inspired lubricating nanosystem with responsive drug release for osteoarthritis therapy

Most of present works of osteoarthritis (OA) therapy are focusing on reducing friction and improving drug loading capacity, while little attention is paid to realizing long-time lubrication and on-demand drug release. In this study, inspired by snowboards with good solid–liquid interface lubrication, a fluorinated graphene based nanosystem with dual functions of long-time lubrication and thermal-responsive drug release was constructed for OA synergetic therapy. An aminated polyethylene glycol bridging strategy was developed to enable covalent grafting of hyaluronic acid on fluorinated graphene. This design not only greatly increased the nanosystem’s biocompatibility, but also reduced the coefficient of friction (COF) by 83.3 % compared to H2O. The nanosystem showed long-time and steady aqueous lubrication behavior even after more than 24,000 times of friction tests, and a low COF of 0.13 was obtained with over 90% wear volume reduction. Diclofenac sodium was controllably loaded and sustained drug release was tuned by near-infrared light. Moreover, anti-inflammation results showed that the nanosystem had good protective effect on inhibiting OA deterioration, which could up-regulate cartilage anabolic genes of Col2α and aggrecan while down-regulating catabolic proteases genes of TAC1 and MMP1. This work constructs a novel dual-functional nanosystem that realizes friction and wear reduction with long lubrication life, and shows thermal-responsive on-demand drug release with good synergistic therapeutic effect of OA.

Investigating the effect of operating temperature on the tribo-mechanical behavior of cold rolled superelastic nickel titanium alloy

NiTi alloys are the most important practical shape memory alloys (SMA) with excellent mechanical properties. Austenitic NiTi alloys with superelastic behavior are currently being investigated for load-bearing applications due to their ability to accommodate large elastic strains and better mechanical properties than martensitic SMAs. We conducted dry reciprocating tests against AISI 52100 steel balls to evaluate the tribomechanical behavior of cold-rolled austenitic Ti – 55.7 wt% Ni alloys at various temperatures, including room temperature, 50 °C, 100 °C, and 200 °C. We observed an 18.3% lower friction coefficient with an 86% reduction in wear volume at 200 °C compared to room temperature during reciprocating tests. Material transfer was captured from the steel ball to the NiTi flat at elevated temperatures and from the NiTi flat to the steel ball at lower temperatures. The primary wear mechanisms on NiTi shifted from abrasive to adhesive with increased operating temperature, and the counter balls shifted from adhesive to abrasive. Indentation testing on austenitic NiTi revealed a 12% increase in hardness with a 50% decrease in Young's modulus at 200 °C, resulting in an increased Modell ratio (Hardness/Young's modulus) with increasing temperature. This phenomenon can be attributed to the austenitic NiTi alloy's increased wear resistance with an increase in operating temperature.

Tribochemical synthesis of functionalized covalent organic frameworks for anti-wear and friction reduction

Tribochemistry can be defined as a field dealing with the chemical reactions occurring in the friction zone, capable of catalyzing mechanical and physico-chemical changes in the friction contact area, facilitating the formation of tribo-films, which is also an efficient approach to fabricate novel innovative materials. In this paper, we report the successful synthesis of the silicon oil (SO)-functionalized covalent organic frameworks (COFs) prepared via the tribochemical method when subjected to the reciprocating friction; during the friction process, the rich aldehyde-terminated COFs can bond with amino SO via the Schiff base reaction between aldehyde group and amino group to obtain the desired functionalized COFs (SO@COF-LZU1). The tribochemical reaction progress was tracked through in-situ monitoring of the friction coefficient and the operating conditions during the entire friction process. Noticeably, the friction coefficient continued to decrease until it finally stabilized as the reaction progressed, which revealed the formation of a protective tribo-film. Herein, an approximate tribochemical model was presented, wherein the reaction mechanism was investigated and analyzed by employing structural analysis techniques like magic angle spinning nuclear magnetic resonance (MAS NMR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Furthermore, the tribochemical-induced SO@COF-LZU1 exhibited remarkable tribological performance with a low friction coefficient of 0.1 and 95.5% reduction in wear volume when used as additives of 500SN base oil. The prime focus of our research was on the preparation and functionalization of COF materials via tribochemical reactions, unraveling a new avenue for the rational design and preparation of functional materials.

Synthesis of Eco-Friendly Carbon Dots as Self-Repairing Additives of Polyalphaolefin by Means of a Green Solvation Effect.

The eco-friendly menthol-modified carbon dots (CDs-Menth) were synthesized for the first time and exhibited the particularly promising application potential as additives of polyalphaolefin (PAO4). On the one hand, the CDs-Menth could be well dispersed into PAO4 with excellent and long-term dispersion stability via a convenient and green mean, that is, the solvation effect of petroleum ether. This mean was far more advanced to current strategies such as chemical modifications and adding dispersants. On the other hand, the CDs-Menth as additives possessed not only the duty-bound merits such as the distinguished friction-reducing, anti-wear, and load-carrying functions, but also an amazing ability of self-repairing effect. The repairing rate of lower disc in the ball-on-disc friction pair lubricated with CDs-Menth/PAO4 lubricant (2.5 wt %) was about 19.3% if the friction duration was prolonged from 20 to 120 min. Meanwhile, the wear volume reduction for PAO4 caused by CDs-Menth remarkably increased from 43.5 to 74.6%. By virtue of the self-repairing effect, the CDs-Menth could form the tough and tensile boundary lubrication films on the rubbing surfaces, not only tremendously reducing the friction and wear of friction pair, but also hopefully protecting the friction interfaces from the potential oxidation and corrosion.

Study of the Role of Titanium and Iron Cathodic Cages on Plasma-Nitrided AISI 430 Ferritic Stainless Steel.

In contrast to austenitic and martensitic stainless steels, ferritic stainless steels have a lower hardness and wear resistance but exhibit excellent corrosion resistance. Due to this fact, their use in the aerospace, automobile, and house construction industries is restricted. Several methods have been utilized to enhance the tribological characteristics of ferritic stainless steels. In this work, titanium nitride coating has been carried out by using a cathodic cage of titanium material, and later on, the titanium cathodic cage is replaced by an AISI-304 cathodic cage in a CCPN chamber to form iron nitride coating on AISI-430 ferritic stainless steel coupons through a plasma nitriding process for 4 h at a fixed temperature of 400 °C. The microstructures and mechanical traits of all processed and control coupons were analyzed using scanning electron microscopy, X-ray diffraction, ball-on-disc wear tester, and microhardness tester techniques. The results showed that hardness increased up to 1489 HV with the titanium cage, which is much higher than the hardness of the base material (270 HV). The titanium cage-treated coupons have high layer thickness, smooth surface morphology, and a minimum crystallite size of 2.2 nm. The wear rate was reduced up to 50% over the base material after the titanium cage plasma treatment. The base coupon exhibited severe abrasive wear, whereas nitrided coupons exhibited dominant adhesive wear. In the iron nitride coatings, this effect is also important, owing to the more influential cleaning process in a glow discharge, and the better adhesion with enhanced interlayer thickness is attributed to the fact that the compliance of the interlayer minimizes shear stresses at the coating–substrate interface. The use of a graded interface improves adhesion compared with the case where no interlayer is used but a titanium interlayer of comparable thickness provides a significant increase in measured adhesion. For both titanium and iron nitride films, there is a reduction in wear volume which is a function of interlayer thickness; this will have a substantial effect on wear lifetime. Thus by careful control of the interlayer thickness and composition, it should be possible to improve coating performance in tribological applications.

Machine Learning‐Guided Design of Pearlitic Steel with Promising Mechanical and Tribological Properties

Herein, attempts have been made to design and develop pearlitic steels for application in heavy‐haul rails. The hardness plays a vital role in studying the mechanical and tribological properties, which is theoretically related to the alloying composition of steel. With aid of machine learning (ML) method, the particle swarm optimization (PSO) improved generalized regression neural network (GRNN) is utilized to model the relationship between composition and hardness of pearlitic steel. The results show that the designed steel exhibits superior hardness and mechanical properties with fine pearlite lamellar microstructure. In addition, the wear behavior of the steel and its wear mechanism are systematically studied by tribological testing and electron probe microanalysis (EPMA) observations of worn surface and wear particles. With composition optimization, the wear resistance has further improved as evidenced by the lower friction coefficient and reduction of wear volume. The pearlitic steels exhibit a combined wear mechanism including adhesive wear, abrasion, delamination, and plastic deformation. As a result, the designed steels offer high hardness with very good mechanical and tribological properties which are far superior to previously reported pearlitic steels. This work may assist in developing the appropriate composition to create the desired hardness, mechanical, and tribological properties.

Structural, mechanical and tribological investigations of CNT-316 stainless steel nanocomposites processed via spark plasma sintering

In this work, carbon nanotube (CNT) reinforced 316 L stainless steel (SS) composites were studied for the impact of CNT content on their microstructural, mechanical and tribological behaviour. Carbon nanotube-SS composites were fabricated via spark plasma sintering process at a sintering temperature of 800 °C. The tribological behaviour for pristine and 0.2, 0.5, 1.0, and 2.0 wt% CNT loaded samples was studied by a ball-on-disc tribometer under a normal load of 10 N at 28 °C and 300 °C. Microstructural studies showed grain refinement with the addition of CNT and hence enhancement in hardness and yield strength. The friction coefficients for high temperature tests were found to be lesser than that of room temperature values. Decrease in friction coefficient at high temperature tribotests compared to low temperature case could be attributed to the lubrication effect coming from local melting and CNTs. The lubrication of CNTs coming from its unique shape, aspect ratio, and flexibility. The wear rate was found to decrease with increasing CNT concentration in both cases. For the 2 wt% CNT case, the wear volume at 28 °C and 300 °C were nearly the same due to the lubrication effect. About 25% and 90% reduction in wear volume was observed for 2 wt% CNT sample at room temperature and 300 °C, respectively, when compared to their pristine counterpart. The composited samples showed increased resistance to wear than the pristine and commercial grade at both temperatures. A systematic study on the morphology, structure, hardness, yield strength, elemental composition, and tribology of the composites to understand the structure-property correlation of CNT-steel composite is presented in detail.

Friction and Wear Characterization of Spark Plasma Sintered Hybrid Aluminum Composite Under Different Sliding Conditions

Abstract Friction and wear behaviors of hybrid aluminum matrix self-lubricating nanocomposite, containing varying amount of nano-aluminum oxide (Al2O3) and graphene nanoplatelet (GNP) particles were investigated under dry and boundary lubrication sliding conditions. All the specimens were prepared by ultrasonic probe mixing followed by high-energy mechanical ball milling and spark plasma sintering fabrication route. The objective of this present study is to determine the tribological behavior of GNP as nanoreinforcement under dry and wet lubricating conditions. The wear test was carried out at room temperature on a ball-on-disc reciprocating tribometer with a contact load of 5 N, a frequency of 30 Hz, a stroke of 2 mm, and a sliding distance of 120 m. The chromium-plated chrome steel ball is used as the counter body for tribo-testing. From the results, it has been observed that GNP, as the solid lubricant reinforcement, reduces the friction by 25.33% and 68.14% under dry and wet lubricating conditions, respectively, for the hybrid composite. Reduction in wear volume by 91.15% and 90.50% is observed under dry and wet lubricating conditions, respectively, for the hybrid composite in comparison to the base eutectic Al–Si alloy. The reduction in the coefficient of friction and wear volume for the hybrid composite is attributed to the multilayer two-dimensional GNP nanoparticles that cause easy shearing by forming a conformal protective film layer on the sliding interface. Ultra-mild to severe wear regime was obtained for different composition samples including base composition to hybrid composition.

Friction and wear properties of a sulphurized layer formed by low-temperature ion sulphurization on a surface nanocrystallized layer

ABSTRACTThe solid lubrication film containing sulphide was prepared on the surface nanocrystallized surfacing layer by low-temperature ion sulphurizing technology. The microstructure of the sulphurized layer was analysed. The tribological behaviour of the sulphurized layer based on the nanocrystalline layer was investigated in a dry friction condition. The sulphurized layer on the nanocrystalline layer has high sulphide content, with the FeS phase accounting for a large proportion of this layer. The sulphurized layer based on the nanocrystalline layer is thicker and denser and has a significantly lower friction coefficient than the untreated sample, with 25% reduction in wear volume. Analysis demonstrated that the high active nanocrystalline layer is also beneficial for the formation of a sulphurized layer. In addition, the high-hardness nanocrystalline layer provides an excellent support for the lubricating layer and is beneficial for enhancing the antifriction property.

Effect of Load on the Tribological Properties of Eutectic Al-Si Reinforced n-Al2O3 under Dry Sliding Conditions

Advanced composites are the materials of the new generation. Hence, the focus of the study is to determine the tribological properties of the eutectic Al-Si alloy reinforced with (2, 4, 6, 8, and10 wt. %) of n-Al2O3 against chrome-plated steel ball under dry sliding conditions. The novelty of this work is the fabrication of the composite sample with this elemental composition, which is not done before. Spark plasma sintering (SPS) nonconventional fabrication method is used to fabricate advanced composite samples. Friction coefficient (COF) and wear rate of the composite samples were studied under high load, varying from 50 N to 300 N, using the ball-on-disc tribometer configuration, with other parameters such as stroke, frequency, sliding distance, and sliding velocity remaining constant at 2 mm, 30 Hz, 120 meter, and 0.120 m/s, respectively. Reduction in wear volume for the advanced composite was reported in the range 15.45–44.58% compared to the base alloy (eutectic Al-Si alloy). An increase in friction coefficient was reported in the range 28.80–35.65% compared to the base matrix alloy material. It was also reported that the wear rate increases and the friction coefficient of the composite sample decreases with an increase in load for the tribo-pair. It was observed that an increase in the wt. % of reinforcement influences the friction and wear behavior of the composite. Wear mechanism at high load was characterized by plastic deformation, adhesion, delamination, and abrasion wear. For pre- and postcharacterization of surface and worn tracks, scanning electron microscopy (SEM) electron dispersion spectroscopy (EDS), 3D surface profilometer, and optical microscopy were used. This work aimed to investigate the influence of load on the tribological properties of Al-Si eutectic reinforced n-Al2O3 under dry sliding conditions. Its main objective was to provide a new contribution to the tribological behavior of these composites fabricated using the nonconventional spark plasma sintering method.

Experimental investigation on dry sliding wear resistance of recently developed hyper-duplex stainless steel

Abstract Duplex stainless steels (DSS) are used in a wide range of industries, predominantly because of the high strength and corrosion resistance they possess. ASTM A890 grade 7A is the newest addition to the family of duplex stainless steels with a unique composition having small amount of rare earth elements. This work is aimed at comparing the sliding wear behaviour of commercially used 5A, 6A and recently developed 7A grades of duplex stainless steel at high sliding velocities. The wear tests were conducted on pin-on-disk apparatus at varying load conditions. Three-dimensional surface analysis of the three grades were conducted using a 3D profilometer to study and compare the roughness of the worn surfaces. Weight loss method used to determine the material removal showed the highest weight loss for grade 5A followed by that of 6A and 7A grades. Grade 7A showed a large reduction in wear volume compared to the other grades. 3D profilometer studies of the worn surface at a load of 60N showed slight plastic deformation in all three grades. Grade 7A showed lower roughness also compared to previous grades

Effect of carbon black nano-fillers on tribological properties of Al6061-Aluminium metal matrix composites

Abstract Nano-metal-matrix composites (NMCs) are novel composite materials in which nano-phase such as nano-particles, nano-rods, nano-structured materials are reinforced with metals or alloys to improve the physical, mechanical, wear and other properties. The results of previous works have shown that the addition of nanoclay reinforcement to aluminium alloys has improved the hardness, tensile strength and Young’s modulus. Hence, the present work is focused on development and characterisation of nanoclay reinforced NMCs. Evaluating the effect of the reinforcement on the important physical properties such as wear property studies were carried out. The wear results exhibited reduction in wear volume compared to the unreinforced alloy specimens and the coefficient of friction is lower at higher loads. The wear loss of MMCs as well as the matrix alloy increased with the increase in applied load.

Improved wear resistance and mechanical properties of multifunctional polymer nanocomposites for advanced engineering applications

Improvement of wear behaviour and mechanical properties of polymers as bulk and surface coating materials for advanced engineering applications have been research interest. Improved wear resistance and mechanical properties were achieved in this study by incorporation of surface modified graphene and titanium dioxide nano-powder in poly (vinylidene fluoride) matrix via solution blending and melt compounding. The morphology of the nanocomposites was studied using scanning electron microscope (SEM). The nanocomposites showed significant reduction in wear volume and enhanced mechanical properties due to the presence of surface modified nanofillers. About 76.5% reduction in wear volume, 52% and 186.5% increase in tensile strength and Young modulus respectively were achieved in this study. The surface modification of the nanofillers was essential in dispersion of the nanofillers in the polymer matrix and the improved properties recorded. Such nanocomposites can find applications as protective surface coating materials for high frictional condition and bulk materials for automobile and aerospace components.

Effect of Boron Carbide on Tribological properties of Zinc Aluminium Metal matrix composites

Metal-Matrix Composites (MMCs) are novel composite materials in which nano/micro-phase such as particles or rods like structured materials are reinforced with metals or alloys to improve the physical, mechanical, wear and other properties. The results of previous works have shown that the addition of B4C reinforcement to aluminium alloys has improved the hardness, tensile strength and Young’s modulus. Hence, the present work is focused on development and characterization of B4C reinforced MMCs. evaluating the outcome of the reinforcement on the physical properties such as wear property studies were carried out. The wear results exhibited reduction in wear volume compared to the unreinforced alloy samples and the coefficient of friction is beneath at lofty loads.

Investigation on the lubrication potential of graphene oxide aqueous dispersion for self-mated stainless steel tribo-pair

Due to high concerns for environmental protection and resource conservation, water-based lubrication with some additives is gaining the attention of researchers. Hence, the present study has been conducted to explore the tribological potential of lubricant containing graphene oxide (GO) as an additive in water. The friction and wear performance was evaluated for self-mated SS 304 under reciprocating sliding using a ball-on-disc configuration under high contact stress (∼1.42 GPa or higher). The results indicate that 0.1 wt% is the optimum content of graphene oxide under the conditions used in the study and has the capability to reduce friction coefficient from 0.56 (pure water) to 0.12 with an attendant reduction in wear volume by 68%. The enhancement in tribological performance has been attributed to the formation of a low shear strength tribo-layer of graphene on the surface of both the ball and the disc. The effect of normal load and sliding speed for optimized concentration was also investigated. The average coefficient of friction was observed to increase with load whereas, it was observed to decrease with increase in speed till 0.05 m/s beyond which it increased.

Lipophilic polymethacrylate ionic liquids as lubricant additives

Despite the growing research field of polymeric ionic liquids used as materials for electrolytes and energy materials, catalysts, separation aides, and carbon materials, reports of lipophilic polymeric ionic liquids for lubricants are essentially nonexistent. Oil-miscible single molecule ionic liquids (ILs) are reported to perform well as neat lubricants and as additives in lubricating base oils. In this work, methacrylate type ionic liquid monomers containing ammonium or imidazolium cations and two different counter-anions were synthesized and used as co-monomers to obtain functional poly(alkyl methacrylates) (PAMAs) as viscosity index improvers (VII) additives for lubricants. The structure of the IL, including the cation, the anion, and the spacer’s length separating the IL from the methacrylate group, plays an important role in the resulting polymer solubility in PAO (poly-alpha olefin), solution rheology, friction, and wear behavior. Depending on the IL structure, VIIs containing up to 20% mol IL are soluble in PAO (grade 4), and demonstrate frictionandwear reduction, compared to a conventional oil-soluble PAMA. Notably, wear volume reduction of up to 80% compared to the oil-soluble control poly(dodecyl methacrylate) is observed.

What is the effect of lipophilic polymeric ionic liquids on friction and wear?

In this work, methacrylate-type ionic liquid (IL) monomers containing a quaternary ammonium cation and two different counter-anions were synthesized and used as co-monomers to obtain functional poly(alkyl methacrylates) (PAMAs). They were then evaluated as friction and wear reducing additives for lubricants. The effect of molecular weight, polymer topology (random or diblock), and IL counter anion on friction and wear behavior of polymer PAO (poly-alpha olefin) solutions have been investigated. The results were compared to those of PAO solutions additized with a small molecule, non-polymeric ionic liquid, or non-ionic copolymers containing 2-(dimethylamino)ethyl methacrylate (DMAEMA) as the polar comonomer. No clear correlation between polymer molecular weight and friction or wear behavior was observed. Random ionic liquid copolymers led to lower wear volumes than their block counterparts. Polymers containing dicyanamide (DCA) counter anion showed lower wear volume compared to those containing bis((trifluoromethyl)sulfonyl)imide (TFSI) anion. Surprisingly, none of the IL copolymers studied outperformed the DMAEMA containing block copolymer in terms of wear volume reduction, suggesting the IL moiety had no beneficial effect on wear.

Experimental Investigations to Enhance the Tribological Performance of Engine Oil by Using Nano-Boric Acid and Functionalized Multiwalled Carbon Nanotubes: A Comparative Study to Assess Wear in Bronze Alloy

In various mechanical systems, lubricants are generally used to reduce friction and wear; thus, the total energy loss in the mechanical systems can be minimized by the proper enhancement of lubrication properties. In general, friction modifiers and antiwear additives are used to improve the tribological properties of the lubricant. However, the use of these additives has to be phased out due to their fast chemical degradation in their applications and other environmental issues. In recent years, the use of nanoparticles as a potential lubricant additive has received considerable attention because of its excellent mechanical and tribological characteristics. The present work describes the tribological behavior of nano-boric acid, multiwalled carbon nanotubes (MWCNTs), and functionalized multiwalled carbon nanotubes (FMWCNTs) modified with carboxylic acid. These nanoparticles were used to enhance the tribological properties of engine oil (SAE20W40) used to lubricate bronze alloy samples. The performance of these nano-coolants was assessed on a linear reciprocating ball-on-flat tribometer. Results highlight the friction and wear behavior of the nano-boric acid, MWCNTs, and FMWCNTs under three varying parameters such as the effect of nanoparticles concentration, load-carrying capacity, and sliding speed. The addition of nano-boric acid, MWCNTs, and FMWCNTs has significantly improved the tribological properties of the base lubricant. The addition of 0.5 wt.% of nano-boric acid, MWCNTs, and FMWCNTs to the base lubricant has decreased the coefficient of friction by 19.76, 30.55, and 35.65%, respectively, and a significant reduction in wear volume by 55.17, 71.42, and 88.97% was obtained in comparison with base lubricant.

Oil-Lubricated Fretting Behaviors of 304 Stainless Steels under Different Fretting Strokes and Normal Loads

ABSTRACT The influence of oil lubrication on the fretting wear behaviors of 304 stainless steel flat specimens under different fretting strokes and normal loads has been investigated. The results proved that fretting regimes and fretting wear behaviors of 304 stainless steels were closely related to the fretting conditions. In general, the increase in normal load could increase wear damage during sliding wear. However, according to the results, a significant reduction in wear volume and increase in friction coefficient was observed when the normal load was increased to critical values of 40 and 50 N at a fretting stroke of 50 μm due to the transformation of the fretting regime from a gross slip regime to partial slip regime. Only when the fretting stroke further increased to a higher value of 70 μm at 50 N, fretting could enter the gross slip regime. There was low wear volume and a high friction coefficient when fretting was in the partial slip regime, because oil penetration was poor. The wear mechanisms were fatigue damage and plastic deformation. There was high wear volume and low friction coefficient when fretting was in the gross slip regime, because the oil could penetrate into the contact surfaces. Unlike the wear mechanisms in the partial slip regime, fretting damage of 304 stainless steels was mainly caused by abrasive wear in the gross slip regime.