Electrochemical Effects on the Corrosion-Wear Behaviors of NiCrMo-625 Alloy in Artificial Seawater Solution

In this article, the tribocorrosion behaviors of NiCrMo-625 alloy sliding against an Al₂O₃ pin using a pin-on-disk tribometer have been carried out to assess the effect of electrochemical state on the corrosion–wear properties of the alloy in artificial seawater. The results shows that a cathodic shift in the open circuit potential of NiCrMo-625 alloy during tribocorrosion is confirmed and a marginal increase in corrosion current can be found under tribocorrosion compared to static corrosion. Total material loss of NiCrMo-625 alloy during tribocorrosion obviously increases with an increase in applied potential, indicating the synergistic effect between wear and corrosion. Although the corrosion rate of the alloy is significantly increased by sliding, the ratio of wear-induced corrosion to the total wear loss is not very large. The proportion of wear-induced corrosion and corrosion-induced wear to the total material loss increases obviously with an increase in potential.     

Effects of cathodic protection on corrosive wear of 304 stainless steel

Corrosive wear involves interaction of electrochemical and mechanical processes. The synergism of these two processes often results in significant material loss, compared to those caused by individual processes. Reduction of either corrosion or wear may effectively decrease material loss under certain circumstances. Since cathodic protection can reduce corrosion of metallic materials, it may also diminish corrosive wear if the corrosion process is suppressed. However, under a cathodic potential (potentiostatic condition) or enforced current (galvanosatic condition), properties of a material could be affected and thus its corrosive wear behavior could be different from what is expected. The present research demonstrated that cathodic protection under potentiostatic condition was beneficial under low wearing force but it became ineffective under higher wearing forces or more negative cathodic potentials. Hydrogen embrittlement could be responsible for this change.     

Assessing the corrosion–wear behaviours of Hastelloy C276 alloy in seawater

A systematic investigation has been carried out in the present work to study the electrochemical and corrosion–wear behaviours of Hastelloy C276 alloy sliding against Al₂O₃ pin in artificial seawater, using a pin‐on‐disc tribometer integrated with a potentiostat for electrochemical control. It can be observed that the cathodic shift of open circuit potential and three order of magnitude increase of current density formed due to sliding. The total corrosion–wear loss increases with increasing applied potential. Interestingly, the total material loss at the applied potential of 0.5 and 0.9 V is more than two times of that of pure mechanical wear, confirming the synergy between wear and corrosion. And, the contributions of wear‐induced corrosion (ΔK_c) and corrosion‐induced wear (ΔK_w) are dominant, especially at higher applied potentials. Copyright © 2015 John Wiley & Sons, Ltd.     

Assessing the Tribocorrosion Performance of Three Different Nickel-Based Superalloys

Tribocorrosion, which is a material deterioration caused by the synergistic effect of corrosion and wear acting together, is encountered in many engineering applications. Ni-based superalloys, which are widely used in chemical, petrochemical and nuclear power industries as well as in hot sections of turbine engines, owing to their excellent corrosion resistance, high strength and capability to retain hardness at elevated temperatures, are subjected to corrosive wear in service conditions. Therefore, an understanding of the tribocorrosion behavior of these superalloys allows choosing the right material for specified applications and predicting the material damage. In this study, the tribocorrosion behavior of Hastelloy C2000, Hastelloy G35 and Haynes 625 was studied using different electrochemical test techniques including open circuit potential (OCP) measurement, potentiodynamic and potentiostatic polarization tests under sliding contact in 3.5 wt% NaCl solution. Scanning electron microscopy (SEM) was employed in order to characterize corrosive-wear damage, and the surface profiles of wear tracks were obtained using a high-resolution surface profilometer for calculating wear loss. Also the metal dissolution caused by corrosive wear was detected using an inductively coupled plasma optical emission spectrometer (ICP-OES). Test results indicated that the tribocorrosion performance of superalloys is affected by their elemental composition and microstructural characteristics, which induce changes in mechanical properties. Haynes 625, which has the highest hardness value owing to decreasing grain size, showed less material volume loss than other superalloys in all tests. However, the protective oxide film on Haynes 625 especially thickened in potentiodynamic tests provided inhibition of excessive metal dissolution. Cathodic protection resulted in decreasing material loss, but on the other hand hydrogen intake was observed on cathodically polarized specimens.     

Synergism between corrosion and wear on CoCrMo−Al2O3 biocomposites in a physiological solution

The use of metal matrix composite structures in biomedical implants can be a solution for decreasing the amount of degradation products. Thus, the present work aims to investigate the synergism between corrosion and wear on CoCrMo matrix 10% (vol) Al₂O₃ particle reinforced composites in phosphate buffer solution (PBS) at body temperature. Corrosion behavior was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization. Tribocorrosion tests were performed under open circuit potential, as well as under cathodic and anodic potentiostatic conditions using a reciprocating ball-on-plate tribometer. Results suggest that the addition of Al₂O₃ particles did not create a significant effect on corrosion behavior of CoCrMo alloy, however, it increased the wear resistance and decreased the corrosion kinetics when sliding in PBS solution.     

Effect of applied potential on the tribocorrosion behaviors of Monel K500 alloy in artificial seawater

A systematic investigation has been carried out in the present work to study the electrochemical and tribocorrosion behaviors of Monel K500 alloy sliding against Al₂O₃ pin in artificial seawater. It can be observed that the cathodic shift of open circuit potential and two order of magnitude increase of current density formed due to sliding. The total tribocorrosion volume loss increases with increasing applied potential. Interestingly, the total material loss at applied potential of 0.5 V and 0.9 V is more than three times of that under pure mechanical wear, confirming the synergy between wear and corrosion. The contribution of wear-induced-corrosion (ΔK_c) and corrosion-induced-wear (ΔK_w) are dominant especially at high applied potential.     

Modelling the tribo-corrosion interaction in aqueous sliding conditions

In corrosion wear, one of the most commonly observed phenomena is the synergism where both corrosion and wear are significantly increased by the tribo-corrosion interactions, leading to much greater material losses than produced by the sum of losses by either process alone. However, mechanisms for the synergistic effect are generally not well understood and there has been little effort in modelling synergistic processes. In this paper, mechanisms for the interactions between corrosion and sliding wear of metals are proposed and a mathematical model is developed which incorporates the various factors affecting corrosion wear, including experimental and environmental conditions and material properties. Many of the observed phenomena in corrosion wear can be explained. It also provides a good basis for wear map construction and would be especially useful in carrying out dimensional analyses for constructing such maps.     

TiSiC,TiSiC-Zr,and TiSiC-Cr Coatings—Corrosion Resistance and Tribological Performance in Saline Solution

TiSiC coatings alloyed with Zr and Cr were deposited on Si and 316 L steel substrates by a cathodic arc method in a CH₄ reactive atmosphere. The corrosion and wear behavior of the coatings in 0.9% NaCl solution was investigated. Corrosion resistance of the coatings was evaluated by electrochemical tests. The electrochemical polarization measurements were conducted at room temperature in the potential range ?1 and 1.5 V, with a 0.167 mVs^?1 scan rate. Compared to the uncoated 316 L substrates, the coated ones showed nobler characteristics, with more electropositive corrosion potentials, lower corrosion current densities, and higher polarization resistances. TiSiC-Zr exhibited the lowest corrosion current density (0.62 μAcm^?2) and the highest protection efficiency (69.5%). The tribological performance of the coatings under corrosive conditions (0.9% NaCl solution) was investigated using a ball-on-disc tribometer (6-mm-diameter sapphire ball, 5 N load, 0.15 ms^?1 sliding speed, 400 m sliding distance). The TiSiC-Cr coating demonstrated the best wear behavior, with a wear rate of 3.2 × 10^?6 mm³N^?1m^?1, followed by TiSiC and TiSiC-Zr. The morphologies and compositions of the worn surfaces were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) in order to identify the wear mechanism. Corrosion, debris adhesion, and oxidation were found to be the dominant wear processes.     

Tribocorrosion of Stellite 706 and Tribaloy 400 superalloys

Abstract

Co based superalloys such as Stellites and Tribaloys have been extensively used in many engineering applications owing to their inherent superior corrosion and wear resistance and hot hardness property at elevated temperatures. The combined interaction among wear and corrosion which is known as tribocorrosion often results in a significant increase in material loss especially in aqueous environments. In this study tribocorrosion performance of Stellite 706 and Tribaloy T400 was investigated by electrochemical techniques such as potentiodynamic (anodic polarisation) and open circuit potential (OCP) measurement with three electrode electrochemical cell set-up under sliding contact in 3·5% NaCl solution. The effect of friction on anodic polarisation behaviour of superalloys was studied at different loads of 20 and 80 N. During OCP measurements the frequency was increased from 0·5 to 1·5 Hz by an increment of 0·5 Hz. Thus the effect of frequency on tribocorrosion behaviour of superalloys was determined. Tribaloy 400 exhibited greater performance in potentiodynamic polarisation test. On the other hand, Tribaloy 400 was more affected by corrosive wear in OCP measurements as compared to Stellite 706.     

A methodology for the assessment of the tribocorrosion of passivating metallic materials

The synergism between mechanical friction and corrosion may lead to an acceleration of the degradation of materials in sliding contacts exposed to the environment. Electrochemical measurements and sliding tests are proposed as a protocol suitable to decouple the material losses originating from the active material and the passive film, and to identify their electrochemical or mechanical nature. The corrosion resistance of a material, its ability to react onto chemical or mechanical attack, its susceptibility to tribocorrosion and the effect of a passive surface film on the coefficient of friction are evaluated. The proposed tribo‐electrochemical protocol allows to evaluate the potential and risks of applying newly developed materials in sliding contacts, and to support the selection and implementation of materials in industry in applications where corrosion and wear are potential degradation processes. This protocol extends the existing Standard Guide ASTM G 119‐04 ‘Determining Synergism between wear and Corrosion’ for passivating metallic materials. Copyright © 2009 John Wiley & Sons, Ltd.     

Tribocorrosion behaviour of powder metallurgy duplex stainless steels sintered in nitrogen

The combined corrosion–wear of powder metallurgy duplex stainless steels obtained by the mixing of ferritic and austenitic powders in several proportions was studied. All the materials were sintered in a nitrogen atmosphere. Tribological and tribocorrosion behaviour was analyzed using a pin-on-disc. Electrochemical techniques: open circuit potential measurements, potentiodynamic polarization measurements and potentiostatic measurements at passive potential under sliding conditions were used. The obtained results were interpreted and related to microstructural features. The tribocorrion behaviour for powder metallurgy duplex stainless steels was a function of the applied electrochemical potential.     

A block‐on‐ring tribocorrosion setup for combined electrochemical and friction testing

The combined action of corrosion and wear can cause degradation of equipment, and thereby financial losses related to the renewal or repair of damaged equipment. In the food industry, metal degradation is a major concern since metal release eventually can cause health risks for consumers. This study describes a block‐on‐ring testing facility used to determine sliding wear, and additionally allowing for electrochemical measurements, such as potentiodynamic polarization curves and potentiostatic monitoring of current and potential. To verify the reliability and reproducibility of this block‐on‐ring tribocorrosion setup, the tribological and electrochemical behaviour of stainless steel sliding against a ceramic ring in sulphuric acid has been determined. Furthermore, a case taken from the food industry has been examined. The study shows that results made on the described block‐on‐ring testing facility are reliable and can provide improved information about material properties when the material is exposed to combined chemical and mechanical degradation. Copyright © 2007 John Wiley & Sons, Ltd.     

Tribocorrosion in implants—assessing high carbon and low carbon Co–Cr–Mo alloys by in situ electrochemical measurements

Tribocorrosion is defined as the chemical–electrochemical–mechanical process leading to degradation of materials in tribological contact immersed in a corrosive environment. Degradation results from the combined action of corrosion and mechanical loading and it is well-known that synergistic effects can accentuate the wear–corrosion rate. While the role of lubrication in reducing wear has been identified, there are still some key unanswered questions in relation to the importance of wear/corrosion interactions. In this study in situ electrochemical measurements have been made to isolate corrosion and corrosion-enhanced wear/tribology damage mechanisms on high carbon CoCrMo and low carbon CoCrMo alloys. Tests are carried out in three different biological solutions: 50% calf bovine serum, Dulbecco's Modified Eagle's Medium (DMEM) and 0.36% NaCl solution at 37 °C with the specific objective being to attempt to isolate the effects of proteins and amino acid species in wear–corrosion. In this paper, a detailed analysis of corrosion/wear interactions is presented, which facilitates discussion of exactly how corrosion and wear processes interact and the role of the lubricating fluid in this respect.     

Friction and Wear Behavior of Ultra-High Molecular Weight Polyethylene Sliding Against GCr15 Steel and Electroless Ni–P Alloy Coating Under the Lubrication of Seawater

The friction and wear behavior of ultra-high molecular weight polyethylene (UHMWPE) sliding against GCr15 steel and electroless Ni-P alloy coating under the lubrication of seawater was investigated and compared with that under dry sliding and lubrication of pure water and 3.5 wt.% NaCl solution, respectively. It was found that under the lubrication of aqueous medium, the friction and wear behavior of UHMWPE mainly depended on the corrosion of counterface and the lubricating effect of the medium. Because of serious corrosion of counterface by the medium, the wear rates of UHMWPE sliding against GCr15 under the lubrication of seawater and NaCl solution were much larger than that under other conditions, and such a kind of wear closely related to the corrosion of counterface can be reckoned as indirect corrosive wear. However, when sliding against corrosion-resistant Ni–P alloy under the lubrication of seawater, the lowest coefficient of friction and wear rate of UHMWPE were obtained, owing to superior lubricating effect of seawater. Moreover, periodic ripple patterns were observed on the worn surfaces of UHMWPE sliding against GCr15 under the lubrication of seawater and NaCl solution, which were ascribed to the intelligent reconstruction of surface microstructure of UHMWPE upon large plowing effect of the counterface asperities. Based on scanning electron microscopic (SEM) and three-dimensional (3D) profile analyses of the worn surfaces of UHMWPE, a stick–slip dynamic mechanism was proposed to illustrate the pattern abrasion of UHMWPE. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Corrosive Wear Behaviors of Carbon Steels in Oil-Water Fluid

Carbon steel (CS) is the most common material used in oil production. Based on surface wetting state, the corrosive wear behavior of CS in oil-water fluid was investigated. The surface wetting state of the metal in oil-water fluids with different water cut and flow velocity was measured using a specially constructed device. Wear loss, corrosion loss, and corrosive wear loss of the CS samples in different oil-water fluids were measured by a reciprocating corrosive wear tester. The damage morphology of the CS samples was observed using scanning electron microscopy (SEM) and the element distribution on the surface was detected by energy-dispersive X-ray spectroscopy (EDS). The results indicated that the surface water wetting rate of the metal increased with water cut and decreased with flow velocity in the oil-water fluid. Wear, corrosion, and corrosive wear behavior of the CS was related to the surface wetting film and surface reaction film. In this test range, the synergetic action is negative and chlorine embrittlement occurs in the fluid with high water cut and low velocity. The damage mechanism of the CS was abrasive wear with selective corrosion.     

TiCxOy thin films for decorative applications: Tribocorrosion mechanisms and synergism

Recently, tribocorrosion is widely accepted as an interdisciplinary area of research and such studies on various materials are gaining more attention by scientists and engineers due to its practical and economical significances in a wide range of applications. The main objective of the present work were to investigate the tribocorrosion behaviour of single layered titanium oxycarbide, TiC_xO_y, thin films on a reciprocating sliding tribometer, and in the presence of artificial sweat solution at room temperature, by considering the practical usage of such films as a decorative coating on various components.

The films were produced by DC reactive magnetron sputtering, using C pellets incrusted in the Ti target erosion area. A gas atmosphere composed of Ar and O₂ was used. The Ar flow was kept constant, and the oxygen gas flow varied from 0 to 10 sccm. During the wear tests both the open circuit potential and the corrosion current were monitored. Also, electrochemical impedance spectroscopy (EIS) tests were performed before and after sliding process. The modifications on the “native” coating microstructure and/or chemical composition induced by the variation of the deposition parameters were also evaluated and correlated with the wear–corrosion mechanisms occurring in each system.

The corrosion studies, including EIS measurements, exhibited the high corrosion resistance of the TiC_xO_y films, which is clear from the unchanged/constant values of the polarization resistance, before and after the sliding process, at the evaluated potential. The effects of hardness, thickness and structure of the films on their tribocorrosion performance, as a function of oxygen fraction, were studied and an attempt was made to classify them. Two of the eight films (f_O=0.55 and 0.79), considered in the test, demonstrated better tribocorrosion resistance than others. Further, individual and synergistic effects of wear and corrosion on total wear loss were estimated and correlated with tribocorrosion mechanisms.     

Tribological behavior of Cu–6Sn–6Zn–3Pb under sea water,distilled water and dry-sliding conditions

Tribological behaviors of Cu–6Sn–6Zn–3Pb alloy sliding against AISI321 stainless steel under sea water, distilled water and dry sliding conditions are studied on a pin-on-disc tester. Generally, the friction coefficient in distilled water is the largest and the smallest in dry-sliding. However, the wear rate is in the opposite case. The wear mechanism is microplough and plastic deformation in distilled water and under dry-sliding, but much severe in the latter case. In sea water environment, the wear mechanism is microplough, plastic deformation and corrosion. Sea water and distilled water show a cooling effect in comparison with dry sliding, additionally, sea water also has lubricating and corrosive effects.     

Influence of microstructure and texture on the corrosion and tribocorrosion behavior of Ti–6Al–4V

In this paper, the corrosion and tribocorrosion behaviors of Ti–6Al–4V alloy having different phase composition, texture and microstructure was investigated. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements were performed to evaluate the corrosion behavior. Sliding wear tests under anodic and cathodic polarization conditions were made to assess the tribocorrosion properties. SEM, OM, and XRD were used to characterize the microstructure, texture, and morphology of the samples. The corrosion resistance was found to depend on to the microstructure, as well as the texture of the surface. A bi-modal microstructure and prismatic texture showed the best corrosion behavior. However, when corrosion was coupled to sliding wear (tribocorrosion), the hardness was found to be the controlling factor.     

An investigation of the corrosive wear of stainless steels in aqueous slurries

Pumping installations made of stainless steels have been widely used for transporting slurries in chemical process industry. However, knowledge of the attack of stainless steels due to corrosive wear in two-phase liquid-particle flow is still incomplete. This paper studies the behaviors and mechanisms of corrosive wear for two austenitic stainless steels, 24Cr-25Ni-4Mo and 18Cr-12Ni-2Mo, using a rotating disc apparatus made by the authors. The two components, wear by slurry abrasion and corrosion, within the corrosive wear process, are first examined individually. Then the synergistic effect between wear and corrosion is investigated. The research we have done shows that corrosive wear rate of samples is closely related to such factors as the solution, type of abrasive, flow velocity, impingement angle and temperature. In addition, a threshold of flow velocity exists which is called the breakaway velocity V_k, above which the corrosive wear rate increases rapidly. The combined effects of abrasion and corrosion result in a total wear loss larger than the added effects of each process alone. An analytical model is developed which would help to reveal the mechanisms of the corrosive wear processes.     

Assessing the Tribocorrosion Performance of Nickel–Aluminum Bronze in Different Aqueous Environments

Metallic components are frequently subjected to corrosion and tribological impacts during their service period, which results in accelerated material deterioration. In this work, a systematic investigation has been conducted to study the tribocorrosion performance of nickel–aluminum bronze (NAB) in different aqueous environments, using a pin-on-disc tribometer integrated with an electrochemical workstation. Results show that the aqueous environments considerably influence the friction and wear behavior of NAB. The friction coefficient and wear rate are highest in deionized water due to its poor lubricity. When an Al₂O₃ pin slid against NAB in 3.5% NaCl solution and seawater, a positive synergistic effect between wear and corrosion occurred. In addition, the relative contribution of corrosion–wear synergism to the total mass loss is greater in 3.5% NaCl solution than in seawater. Also of note is that applied potential plays a significant role in determining the material degradation.