Greatly enhanced corrosion/wear resistances of epoxy coating for Mg alloy through a synergistic effect between functionalized graphene and insulated blocking layer

The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.

Effects of Yttria Addition on Microstructure,Mechanical Properties,Wear Resistance and Corrosive Wear Resistance of TiNi Alloy

TiNi alloy has a high resistance to wear and could be an excellent candidate for various tribological applications. But studies show that oxygen active elements can improve properties of some alloys, markedly. Yttrium is one of the oxygen active elements. In this paper, the effects of yttria addition on properties of TiNi have been studied via micro-indentation, hardness, wear and corrosive wear tests. It is demonstrated that by addition of yttria to 5%, TiNi alloy can own improved mechanical properties and resistance to wear and corrosive wear.

Effect of SiC content on dry sliding wear, corrosion and corrosive wear of Al/SiC nanocomposites

The corrosion, corrosive wear and dry sliding wear of nanocomposites, are extremely complicated and involve various chemical, physical anbd mechanical factors. The aim of this work is to investigate the effects of nanosized SiC content on the hardness, dry sliding wear, corrosion and corrosive wear of Al/SiC nanocomposites synthesized by mechanical milling cold pressing and hot extrusion. The corrosion resistance of these composites in 3%NaCl solution was investigated by electrochemical polarization testing and their dry sliding as well as corrosive wear resistance in the same solution was evaluated using a pin-on-disc tester. The microstructures of the samples and their worn surfaces were examined using scanning electron microscopy. It was shown that the dry sliding wear and corrosion resistance of these nanocomposites were improved with the increase of SiC content. It was concluded that due to the lubrication effect of the solution, both the friction coefficient and frictional heat that might soften the material were reduced. In addition, the improved strength of the nanocomposites combined with their better corrosion resistance contributed to their increased corrosive wear resistance, compared with the base alloy. The prominent wear mechanism in the unreinforced alloy was adhesive wear, in the Al/SiC nanocomposites, the wear mechanism changed to abrasive.

Effect of molybdenum on the microstructure and corrosive wear resistance of laser clad Ni-based coatings

Five kinds of Ni-based coatings with 0 wt% , 2. 5 wt% , 5.0 wt% , 7.5 wt% and 10. 0 wt% molybdenum were prepared on 45CrNi steel plates by using laser cladding technique. The effect of Mo on the microstructure of Ni-based coatings was investigated by using scanning electron microscopy. The corrosive wear resistance and the corrosion resistance of five coatings were tested. The results show that the corrosive wear resistance of the coating with 5.0 wt% Mo is better than those of other coatings. During the corrosive wear process, the corrosion and wear effects are combined. The corrosive wear resistance is closely related to the microstructure of the coating.

Corrosive-wear and Electrochemical Performance of Laser Thermal Sprayed Co30Cr8W1.6C3Ni1.4Si Coating on Ti6Al4V Alloy

Co30Cr8W1.6C3Ni1.4Si coatings were fabricated on Ti6Al4V alloy using a laser thermal spraying(LTS).The surface and cross-section morphologies,phases and bonding strength of obtained coatings were investigated using scanning electronic microscopy(SEM),X-ray diffraction(XRD),and scratch test,respectively.The effects of laser power on the coefficients of friction(COFs)and corrosive-wear behaviors of Co30Cr8W1.6C3Ni1.4Si coatings were investigated using a wear tester in 3.5%NaCl solution,and the electrochemical corrosion performance was analyzed using an electrochemical workstation.The experimental results show that the Co30Cr8W1.6C3Ni1.4Si coating is bonded with the substrate in the metallurgical form,and the bonding strengths of Co30Cr8W1.6C3Ni1.4Si coatings fabricated at the laser power of 1000,1200,and 1400 W are 76.5,56.5,and 55.6 N,respectively.The average COFs of Co30Cr8W1.6C3Ni1.4Si coatings fabricated at the laser power of 1000,1200,and 1400 W are 0.769,0.893,and 0.941,respectively;and the corresponding wear rates are 0.267×105,0.3178×105,and 0.325×105μm3/Nm,respectively,which increases with the increase of laser power,the wear mechanism is primarily abrasive wear.The corrosion potential of Co30Cr8W1.6C3Ni1.4Si coatings fabricated at the laser power of 1000,1200,and 1400 W is-0.05,-0.25,and-0.31 V,respectively,higher than-0.45 V of substrate which enhances the electrochemical corrosion resistance of substrate.

CORROSIVE WEAR BEHAVIOUR OF ALLOY CD-4MCu IN PHOSP(?)ORIC ACID

The corrosion rate,together with corrosive wear and corrosion coefficient under load,of alloy CD-4MCu in 69% H_3PO_4 or 69% H_3PO_4+500 ppm NaCl solution measured,and the morphology of their wear tracks was then observed by SEM.The alloy CD-4MCu is revealed to be superior in corrosive wear resistance to stainless steel 304 and even to Carpenter 20Cb3,a high corrosion resisting alloy.From its features of duplex phase structure,it could be suggested that the weight loss related to mechanical factor was improved by existence of austenitic phase due to its deformation strengthening.

Effects of Rare Earth Elements on Corrosive Wear Behaviour of Cast Cr-Mn-N Stainless Steel in Dilute Sulphuric Acid

The effects of rare earth elements on the corrosion and corrosive wear resistance of Cr Mn N stainless steel were studied, and the optimal content of RE(%) in the steel was obtained. This work would provide the necessary parameters in producing this kind of stainless steel.

Corrosion and wear properties of in situ(TiB+TiC)/TA15 composites with a high volume percentage of reinforcement

The in situ(TiC+TiB)/TA15 composites with different volume percentages of reinforcement(10%,15%,20%and 25%)were prepared by water-cooled copper crucible vacuum suspension melting technology.The structures and compositions of the TA15 alloy and its composites were analyzed by XRD and EDS,and their electrochemical corrosion behaviors in the 3.5%NaCl solution were studied.Corrosion wear testing was conducted using a reciprocating ball-on-disc wear tester under a 10 N load.Results show that the in situ fibrous TiB phase and the granular TiC phase are uniformly distributed on the composite matrix.The microhardness can reach up to 531 HV as 25vol.%TiC+TiB reinforcement is added.Compared with the TA15 alloy,the volume wear rate decreases from(2.21±0.07)×10^(-4)to(1.75±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1)by adding 15vol.%TiC+TiB reinforcement,and the wear mechanism is adhesive wear.When the volume percentage of the reinforcement phase reaches 25%,the volume wear rate increases from(1.75±0.07)×10^(-4)to(2.41±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1),and the wear mechanism changes into abrasive wear.The volume loss resulted by the interaction between corrosion and wear accounts for more than 27%of the total wear volume.The volume loss due to wear-induced corrosion changes from 1.94%to 4.06%with different additions of reinforcement.The volume loss caused by corrosion-induced wear initially increases from 24.08%to 26.90%as the reinforcement increases from 0 to 15%due to the increase of corrosion potential,and then decreases from 26.90%to 25.68%as the reinforcement increases from 15%to 25%due to the peeling of TiC phase.

Study on wear resistant cast B-containing 1Cr18Ni9Ti stainless steel

The developed 1Cr18Ni9Ti austenitic stainless steel containing 1.63 wt.%B have been characterized by X-ray diffraction(XRD),electron probe microanalyzer(EPMA),optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS)and Vickers microhardness measurement.The microstructural evolution and property of high boron stainless steel after solution treatment at the temperature of 1050℃are also investigated.The results show that the main compositions of borides are Fe,Cr and B,and with small amount of Ni,Mn and C elements.Silicon is insoluble in the borides.The hardness of borides is over 1,500 HV.It has been found that borides do not decompose during solution treatment,but part of borides dissolves into the matrix. The effect of increasing the solubility of boron element in the austenitic matrix favours the hardness enhancement by 8.54%.High boron stainless steel has excellent wear resistance in corrosive environment.Lifetime of transfer pipe made of high boron-containing stainless steel is 1.5-1.8 times longer than that of boron-free 1Cr18Ni9Ti stainless steel.

INTERACTION BETWEEN CORROSION AND WEAR OF STA LESS STEEL IN H_3PO_4+NaCl SOLUTION

Plots of corrosion-wear loss vs load and anodic polarization curves during wearing were for a duplex stainless steel in 69% H_3PO_4 solution with or without Cl^- by a pin-on-disc apparatus.Morphologies of tracks and debris as well as variation of Vicker hardness of worn surface were also examined.The Cl^- may impel the embrittlement and tear of worn surface,so as to accelerate the corrosi-wear loss of the steel.

Effects of Yttrium Addition on Microstructure, Hardness and Resistance to Wear and Corrosive Wear of TiNi Alloy

TiNi alloy has a high resistance to wear and could be an excellent candidate for various tribological applications. In this paper, it was demonstrated that by addition of yttrium, hardness properties and resistance to wear and corrosive wear of TiNi alloy were improved. New yttrium rich regions were formed in microstructure of TiNi alloy. The improved properties of this alloy by the yttrium addition could be attributed to the formation of these regions. The results showed that there was an optimum content for addition of yttrium between 2% and 5% （in wt%）, and above this content the improvement in properties of TiNi became minor.

Adhesive and corrosive wear at microscales in different vapor environments

Adhesive and corrosive wear at microscales are quantitatively distinguished in lifetime tests of resonant bulk-fabricated silicon microelectromechanical systems(MEMS).By analyzing the oscillation decay characteristics in different vapor environments,we find that wear is dominated by asperity adhesion during the initial stages of rubbing in dry N2 or O2/N2 mixtures;in these situations the transient wear rate is inversely proportional to the wear depth.But in water or ethanol vapors,chemical reactions between the corrosive adsorbed layer and the silicon substrate limit the wear rate to a constant.These observations are consistent with atomic explanations.The differences between adhesive and corrosive wear explain the advantages offered by lubricating with alcohol vapors rather than using dry environments for tribo-MEMS devices.Compared to ethanol,the relatively poor anti-wear effect of water vapor is explained by aggressive and rapid tribo-reactions.

Rietveld refinement of powder X-ray diffraction,microstructural and mechanical studies of magnesium matrix composites processed by high energy ball milling

This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy milling.Samples of Mg-SiC and Mg-Al_(2)O_(3)composites subjected to high energy ball milling for different vol%of secondary particles 20,30 and 40%of SiC and Al_(2)O_(3)are studied by X-Ray diffraction technique.The rietveld method as implemented in the Fullprof program is applied in order to determine the quantities of the resulting crystalline phases and amorphous phases at each stage of the mechanical treatment.Microstructural examination is carried out using Scanning Electron Microscope(SEM).In addition,crystal structural analysis using appropriate size and strain models is performed in order to handle the distinctive anistrophy that is observed in convinced crystallographic directions for the magnesium composite.The results are furnished in terms of crystalline domains size enlargement of the magnesium composites phases upon prolonged milling duration and discussed in the light of up to date views and theories on crystal growth of nanocrystaline materials.The hardness of the composite samples is calculated by Vickers’s Hardness tester.Further,dry sling wear test and corrosion test are performed for the fabricated composites.Composite with 30%secondary particles incorporated magnesium composites exhibits better wear and corrosion resistance than the other composites.

Effect of Salt Spray Corrosion on Tribological Properties of HVOF Sprayed NiCr-Cr3C2 Coating with Intermediate Layer

The objective of the present work was to determine the influence of the neutral salt spray corrosion on the wear resistance of HVOF sprayed NiCr-Cr3C2 coating with intermediate layer. Ni-Zn-Al2O3 coatings as interlayers were prepared by low pressure cold spray（LPCS） between NiCr-Cr3C2 cermet coatings to form a sandwich structure to enhance the corrosion resistance properties. The tribological properties were examined using the UMT-3 fricition and wear tester by line-contact reciprocating sliding under dry and salt spray one week corrosion. The morphology, element distribution, and phase compositions of the coating and worn sufaces were analyzed by using scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction respectively. The corrosion behavior of the coating was studied by the open-circuit potential, the electrochemical impedance spectroscopy, potentiodynamic polarization, and salt spray corrosion methods. It is found that the sandwich structured coating has better corrosion resistance than the single layer coating. The results show that under dry wear conditions, the wear mechanism is abrasive and adhesive wear, whereas under salt spray corrosion conditions it becomes corrosion wear. The friction coefficient of the sandwich structured coating after salt spray corrosion is slightly lower than the dry friction coefficient, but the weight of the wear loss is lower than that under dry condition.

Process-structure-property relationship for plasma-sprayed iron-based amorphous/crystalline composite coatings

This study explores the fabrication of Fe-based amorphous/crystalline coating by air plasma spraying and its dependency on the coating parameters(plasma power,primary gas flow rate,powder feed rate,and stand-off distance).X-ray diffraction of the coatings deposited at optimized spray parameters showed the presence of amorphous/crystalline phase.Coatings deposited at a lower plasma power and highest gas flow rate exhibited better density,hardness,and wear resistance.All coatings demonstrated equally good resistance against the corrosive environment(3.5wt%NaCl solution).Mechanical,wear,and tribological studies indicated that a single process parameter optimization cannot provide good coating performance;instead,all process parameters have a unique role in defining better properties for the coating by con-trolling the in-flight particle temperature and velocity profile,followed by the cooling pattern of molten droplet before impingement on the substrate.

Two material removal modes in chemical mechanical polishing:mechanical plowing vs.chemical bonding

With the rapid development of semiconductors,the number of materials needed to be polished sharply increases.The material properties vary significantly,posing challenges to chemical mechanical polishing(CMP).Accordingly,the study aimed to classify the material removal mechanism.Based on the CMP and atomic force microscopy results,the six representative metals can be preliminarily classified into two groups,presumably due to different material removal modes.From the tribology perspective,the first group of Cu,Co,and Ni may mainly rely on the mechanical plowing effect.After adding H_(2)O_(2),corrosion can be first enhanced and then suppressed,affecting the surface mechanical strength.Consequently,the material removal rate(MRR)and the surface roughness increase and decrease.By comparison,the second group of Ta,Ru,and Ti may primarily depend on the chemical bonding effect.Adding H_(2)O_(2)can promote oxidation,increasing interfacial chemical bonds.Therefore,the MRR increases,and the surface roughness decreases and levels off.In addition,CMP can be regulated by tuning the synergistic effect of oxidation,complexation,and dissolution for mechanical plowing,while tuning the synergistic effect of oxidation and ionic strength for chemical bonding.The findings provide mechanistic insight into the material removal mechanism in CMP.

Hierarchical Ti_(3)C_(2)T_(x)@MoS_(2) heterostructures:A first principles calculation and application in corrosion/wear protection

Surface and interface engineering plays a crucial role in modulating the properties of materials,especially two-dimensional(2D)materials.Hence,a strategy,forming heterostructures with MoS_(2),is proposed to overcome the natural agglomeration of Ti_(3)C_(2)T_(x) MXene nanosheets.Most importantly,the interactions between Ti_(3)C_(2)Tx and MoS_(2) were elaborately investigated by first-principles calculations based on density functional theory(DFT)for the first time.The calculations demonstrate that van der Waals forces dominate the interface interactions of Ti_(3)C_(2)T_(x) and MoS_(2),rendering Ti_(3)C_(2)T_(x)@MoS_(2) heterostructures favorable stability.The Ti_(3)C_(2)T_(x)@MoS_(2) heterostructure composites were synthesized through a facile one-step hydrothermal method and exhibit a 2D hierarchical structure.Furthermore,the corrosion and tribological properties of epoxy composite coatings with varying proportions of Ti_(3)C_(2)T_(x)@MoS_(2) composites were studied in detail.As a result,the epoxy composite coating with 0.1 wt.%Ti_(3)C_(2)T_(x)@MoS_(2) composites(Ti_(3)C_(2)T_(x)@MoS_(2)-0.1)exhibits excellent corrosion protection and antiwear performances.The Ti_(3)C_(2)T_(x)@MoS_(2)-0.1 keeps the largest low-frequency impedance modulus(|Z|_(0.)01 Hz)and coating resistance(R_(c))during the whole immersion period.Its wear rate is 0.09μm^(3)/(Nμm)under the load of 10 N,one half of that of pure epoxy coating(EP).This work further broadens the application of MXene-based heterostructure composites.

Tribo-corrosion interaction of the parallel steel wires in the suspension bridges

The effect of contact load and relative displacement on tribo-corrosion interaction of parallel steel wires of main cable in the suspension bridge was investigated in this study.A self-made tribo-corrosion test bench was employed to conduct tribo-corrosion tests of parallel steel wires in 3.5%(wt%)NaCl solution and deionized water under different contact loads and different relative displacements.The friction coefficient and wear coefficient of wires were presented.Electrochemical corrosion behavior(Tafel polarization curves,Nyquist diagram,and equivalent circuit diagram)was characterized by electrochemical analyzer.Wear morphology was observed by scanning electron microscope.Wear volume loss and corrosion‒wear interaction were quantitatively demonstrated by high-precision weighing balance.The results show that the electrochemical corrosion ability of the steel wires increases with the increase of the contact load or relative displacement.The increased contact load or relative displacement increases the volume loss of corrosion‒wear and pure wear,but decreases the wear coefficient.The wear mechanisms in 3.5%NaCl solution are adhesive wear,abrasive wear,and corrosive wear as compared to adhesive wear and abrasive wear in deionized water under different contact loads.The wear mechanisms of parallel steel wires are slightly different under different relative displacements.But the main wear mechanisms are similar to that under different contact loads.The interaction effects of corrosion and wear produced by the contact load and relative displacement are all the synergistic effects.

Mitigation of tribocorrosion of metals in aqueous solutions by potential-enhanced adsorption of surfactants

Corrosion and corrosive wear occur commonly on metals surface in aqueous solutions.External electric field is usually considered as one of the factors to accelerate corrosion or corrosive wear of materials in the presence of conventional electrolytes.This work aims to reposition widely believed perspective by experimental justification which have been conducted in aqueous solutions containing surfactants.Electric potential of metal surfaces was modulated externally within the electrochemical potential window of the metal electrode-solution-counter electrode system,which actively regulated the adsorption or desorption of surfactant molecule in the aqueous solution over the electrodes to form a molecular barrier of electron transportation across the electrode–electrolyte interface.The advantage of the approach over the anodic passivation is negligible redox reactions on the protected electrode surface while a better lubricious and wear resistant film than oxide is maintained in the meantime.Tribopairs of several metal/metal and metal/ceramic were tested by employing a ball-on-disc tribometer with anionic and cationic surfactants solutions.For anionic surfactant as the modifier,positive surface potential enables coefficient of friction to be decreased by promoting the formation of adsorption film on metal surface in aqueous solutions.For cationic surfactant,negative surface potential plays a role in decreasing the coefficient of friction.Phase diagrams of friction and wear in wide ranges of surfactant concentration and surface potential were plotted for the tested metal/metal and metal/ceramic tribopairs.These results indicate that the adsorption behavior of molecules or ions at the metal–aqueous interface can be well regulated when an external electric field is present without inducing corrosion or corrosive wear.

Effect of environments and normal loads on tribological properties of nitrided Ni(45)(FeCoCr)(40)(AlTi)(15)high-entropy alloys

The tribological properties of nitrided Ni(45)(FeCoCr)(40)(AlTi)(15)high-entropy alloys(HEAs)were investigated in air and simulated acid rain under different normal loads(5,7,10,and 12 N)at ambient temperature.The results revealed that as-cast HEAs were only composed of FCC phase,while the volume fraction of FCC phase in the nitrided alloys was significantly reduced.Moreover,the hard phases of AIN,CrN,Fe4 N,and TiN phases were formed in the nitrided alloys.The thickness of the nitriding layer was about 8.4μm.The hardness increased from 8.7 GPa in as-cast alloys to 14.5 GPa in the nitrided alloys.In addition,under the same conditions,the friction coefficient of the nitrided alloys was higher than that of as-cast alloys,but the wear rate was generally lower than that of as-cast alloys.Furthermore,the wear rate of the nitrided alloys was the lowest in acid rain due to the lubrication,cleaning,and cooling in the liquid environment.In air,dominating wear mechanisms in as-cast and nitrided alloys were abrasive,delamination,and adhesive wears.And,the wear mechanism of as-cast and nitrided alloys in acid rain was mainly abrasive and corrosion wears.