Tribocorrosion Response Research Articles

Comparative investigation on the tribocorrosion resistance of Ti6Al4V and 60NiTi alloys inimulated seawater environment

The Ti6Al4V alloy is extensively utilized in critical marine equipment components due to its low density, high specific strength, and exceptional corrosion resistance in marine environments. However, its low hardness and inadequate wear resistance pose challenges in meeting the urgent demand for prolonged service life of relative motion friction pairs under complex wear and corrosion conditions. As a newly developed lightweight friction pair material, hardened 60NiTi is considered highly desirable owing to its combination of high hardness, high compressive strength, and excellent corrosion resistance. Nevertheless, the tribocorrosion properties of 60NiTi compared to those of Ti6Al4V are not yet fully comprehended. The present study conducted a series of sliding wear tests using a ball-on-plate configuration in artificial seawater environment to compare the response of 60NiTi with Ti6Al4V. In order to gain a comprehensive understanding of the factors contributing to the divergence in tribocorrosion response between both materials, further analysis was performed on the wear track subsurface and transfer film using focused ion beam-scanning electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy respectively. The 60NiTi demonstrates significantly enhanced wear resistance in artificial seawater compared to Ti6Al4V, attributed to its combination of high hardness and excellent corrosion resistance. However, Ti6Al4V exhibits a lower friction coefficient (∼0.30) than 60NiTi (∼0.45) due to the formation of a stable transfer film primarily composed of SiO2, Al(OH)3, and Al2O3.

Tailoring the tribo-corrosion response of (CrNbTiAlV)CxNy coatings by controlling carbon content

High-entropy carbonitrides exhibit excellent properties in friction and corrosion. Here, the tribo-corrosion response of (CrNbTiAlV)CxNy coating were studied in 3.5 wt.% NaCl solution at room temperature. The doping of carbon makes the coating structure dense. When the carbon content of the coating is 40%, the coating exhibits maximum hardness (20.21 GPa). As the carbon content increases, the synergistic effect of tribo-corrosion on the coating gradually weakens, and friction coefficient decreases. The coating with 40% carbon content has the smallest change in static and dynamic current density (0.14 ×10−8 A/cm2), the smallest friction coefficient (0.28), and the smallest wear volume loss. These results show that the coating can effectively protect the substrate in case of tribo-corrosion.

A tribocorrosion appraisal of a dual layer PVD coated CoCrMo alloy tribopair

A dual layer PVD coating consisting of a CrN layer on top of a CoCrMo(C) S-phase underlayer (CrN/S) was deposited on low-carbon wrought CoCrMo alloy discs and CoCrMo Stellite® 21 spheres. The tribocorrosion response of the uncoated CoCrMo tribopairs and coated CrN/S tribopairs was studied under reciprocating sliding conditions in Ringer's and diluted foetal bovine serum (FBS) solutions under anodic potential and elastic contact for a sliding time of 2 h. Compared to the uncoated tribopair, CrN/S successfully mitigated both oxidation and mechanical material losses and resulted in a low dynamic coefficient of friction and smoother scar morphologies in both test solutions. For the uncoated tribopair, the presence of proteins acted as a barrier to charge transfer and lowered the friction during tribocorrosion testing contributing to a marked reduction in material loss, primarily by a reduction in oxidative losses, but resulted in a rougher scar morphology. Tribocorrosion tests of the coated tribopair were also carried out for a duration of 24 h and revealed minimal material losses in diluted FBS and no evidence of other damage. It, however, resulted in substantial thinning of the outer CrN layer, transverse microcracking and delamination when testing in Ringer's solution. This coating loss produced a source for coating debris which led to three-body micro-abrasion damage. FIB investigation revealed that the observed transverse microcracks were limited to the outer layer and hence have not provided electrolytic pathways to the substrate interface. The excellent tribocorrosion response of dual layer CrN/S on CoCrMo metal tribopairs in diluted FBS renders them good candidates for further investigation to mitigate tribocorrosion damage of biomedical CoCrMo alloys.

Tribo-corrosion response of additively manufactured high-entropy alloy

High-entropy alloys (HEAs) with multiple principal elements represent a paradigm shift in structural alloy design and show excellent surface degradation resistance in corrosive environment. Here, the tribo-corrosion response of laser-engineered net-shaped CoCrFeMnNi HEA was evaluated in 3.5 wt% NaCl solution at room temperature. The additively manufactured (AM-ed) CoCrFeMnNi showed five times lower wear rate, regenerative passivation, and nobler corrosion potential during tribo-corrosion test compared to its arc-melted counterpart. A significant anisotropy was seen in the tribo-corrosion response with 45° to the build direction showing better performance compared to tests along the build direction and perpendicular to it. The open circuit potential curves were characterized by a sharp drop to more negative values as wear began, followed by continuous change for the active tribo-corrosion duration and finally a jump to nobler value at the end of the test indicating excellent surface re-passivation for the AM-ed alloy. The superior tribo-corrosion resistance of AM-ed CoCrFeMnNi was attributed to the refined microstructure and highly protective surface passivation layer promoted by the sub-grain cellular structure formed during additive manufacturing. These results highlight the potential of utilizing additive manufacturing of HEAs for use in extreme environments that require a combination of tribo-corrosion resistance, mechanical durability, extended service life, and net shaping with low dimensional tolerance.

The effect of the substrate surface state on the morphology, topography and tribocorrosion behavior of Si/Zr sol-gel coated 316L stainless steel

In the present work, a Si/Zr based sol–gel (SG) coating was deposited on 316L stainless steel plates, previously treated by passivation (SSO) or electropolishing (SSEP) producing two different surface states. The SG coatings were compared for SSO and SSEP substrates in terms of morphology, topography and tribocorrosion response. The coating topography revealed a smoother surface for the Si/Zr-SSEP system. The coating deposited on the smoothest surface (Si/Zr-SSEP) presented half of the thickness of the one deposited on the roughest surface (Si/Zr-SSO). Tribocorrosion behavior was studied under potentiostatic control at anodic potential with a continuous recording of current (I) during sliding (pin-on-disc and alumina ball counterbody). Both SG systems showed an increase of current upon 100 sliding contact cycles indicating corrosion activity. After tribocorrosion tests, both systems revealed scratches, typical of abrasion, and coating removal in the wear tracks; the alumina counterparts presented accumulation of wear particles adhered to their surfaces. In conclusion, the initial surface state of the substrate modified the coating thickness, topography but did not significantly alter the tribocorrosion response of the studied SG systems.

Preliminary tribocorrosion evaluation of bio-functionalized Ti doped with Ca-P-Sr

Micro-arc oxidation is being applied to overcome the poor wear resistance of Ti that also enables to give bio-functions with the incorporation of bioactive agents such as Ca, P and Sr. In the present work, micro-arc oxidation was used to obtain Ca-P-Sr-doped hard TiO2 porous layers with three different amounts of Sr and tribocorrosion behaviour was investigated. Results showed that the distribution of anatase and rutile in the porous oxide layer led to a less visible damage and lower COF values, where the group containing more Sr presented the best tribocorrosion response mainly due to the increased amount of rutile.

Impact of industrially applied surface finishing processes on tribocorrosion performance of 316L stainless steel

This investigation addresses the effect provided by industrial surface finishes on the tribocorrosion properties of 316L stainless steel exposed to NaCl solution. Three distinct surface treatments were evaluated: passivation (SSO), electropolishing-passivation (SSEP) and micro-undulation (SSM mechano-chemical + electropolishing + passivation). For the tribocorrosion tests, a potentiostatic approach was considered in order to highlight the alloy behavior under two opposite situations, where repassivation of the surface would be thermodynamically possible or not (anodic or cathodic polarization, respectively). The outcomes demonstrated that the surface treatments were either harmful (SSEP) or beneficial (SSM) in terms of resulting tribocorrosion resistance. The specific topography of the micro-undulated sample decreased the real contact area and improved the surface lubrication in aqueous medium. SSEP presented the highest chemical wear and several factors seemed to have contributed for it, including the chemical, mechanical and structural properties of the passive film. Regardless the surface treatment, the tribocorrosion response was modified by the applied potential and more severe damage was determined under anodic polarization. At this potential, calculations of the total surface degradation suggested that volume loss was mainly dominated by chemical wear.

Tribocorrosion response of duplex layered CoCrMoC/CrN and CrN/CoCrMoC coatings on implant grade 316LVM stainless steel

The objective of this work was to improve the tribocorrosion performance of biomedical grade 316LVM stainless steel via the application of duplex layered coatings. Two different PVD coatings were deposited via magnetron sputtering: (1) an underlying CoCrMo carbon S-phase layer followed by an outermost CrN layer designated as CrN/S and; (2) an underlying CrN layer followed by an outermost CoCrMo carbon S-phase designated as S/CrN. Tribocorrosion of the coated and uncoated 316LVM was studied against an alumina ball which was made to slide in a reciprocation motion in Ringer's solution. The contributions of wear, corrosion and their synergy were elucidated by performing tests under open circuit, cathodic and anodic potential conditions. The resultant wear scars were analysed via SEM, EDS, optical microscopy and contact profilometry. Both coatings displayed superior tribocorrosion response to AISI 316LVM with CrN/S exhibiting the best performance. CrN/S displayed lowest coefficient of friction under all electrochemical conditions (~0.10–0.15) and a material loss under anodic condition with a 93% decrease when compared to 316LVM. The CrN/S scars exhibited a smooth morphology under all test conditions in contrast with the other two test materials which displayed shearing marks oriented along the sliding direction under OCP and anodic conditions. By considering the resultant scar morphologies, a hypothesis is being proposed to explain the tribocorrosion degradation mechanisms encountered.

Tribocorrosion behaviour of pure titanium in bovine serum albumin solution: A multiscale study

Tribocorrosion behaviour of pure titanium in phosphate buffer saline (PBS) solution has been investigated systematically as a function of surface chemistry and bovine serum albumin (BSA) content in the solution. A ball-on-disk tribometer coupled with an electrochemical cell was used to study the effect of electrochemical conditions (i.e. anodic and cathodic applied potentials, as well as at open circuit potential) on the tribocorrosion response of titanium. It was found that the main material loss is due to mechanical wear caused by plastic deformation. The mechanical wear was higher under anodic conditions than under cathodic, partially due to an increased presence of debris particles at the sliding interface that act as third bodies. The effect of BSA on the interaction between alumina and titanium, as well as the behaviour of third bodies during the mechanical wear, were investigated in the nanoscale level using atomic force microscopy based force spectroscopy. It was found that the presence of BSA affects tribocorrosion in various ways. Firstly, it increases the repassivation rate of the oxide film by inhibiting the cathodic reactions and accelerating the anodic reactions. Secondly, it increases the mechanical wear by increasing the adhesion of debris onto the sliding interface, while at anodic conditions it increases the rolling efficiency of the debris particles that further enhances the mechanical wear.

Low Stress Abrasion-Corrosion of High-Cr White Cast Iron: Combined Effects of Particle Angularity and Chloride Ions

Tribo-electrochemical behavior of a high chromium white cast iron (high-Cr WCI) used in, e.g., slurry pumps in mining and mineral processing applications, was investigated using a combination of electrochemical techniques, including zero resistance amperometry as well as potentiostatic and potentiodynamic polarisation. The effects of third body particles angularity on the localised tribocorrosion response of the cast alloy was studied during and post abrasion-corrosion by round ceramic beads and semi-angular silica sand particles. Advanced characterization methods such as electron backscatter diffraction and focused-ion beam cross-sectioning of affected areas were also employed to understand the wear and corrosion interactive actions. It was found that in chloride-free solutions, the behavior of high-Cr WCI resembled that of the austenitic 316 SS studied before. In contrast, in chloride-containing electrolytes, the semi-angular silica sand particles increased interfacial (carbide/matrix) localised corrosion susceptibility during and post-abrasion as indicated by the stark increase in anodic current and the morphology of the attack. Semi-angular silica sand abrasives had a greater adverse impact on post-abrasion interfacial corrosion vulnerability, compared to round ceramic beads. The complex behavior observed indicates that any material developed for tribocorrosive conditions must account for the particles angularity and their subsequent effects on localised corrosion.

Tribocorrosion Response of Surface-Modified Ti in a 0.9% NaCl Solution

Titanium use is limited due to its poor tribological properties, and thermal oxidation (TO) and pack carburisation with limited oxygen diffusion (PCOD) are just two of the surface treatments that can be used to enhance the surface properties of Ti. In this study, commercially pure titanium was surface modified using thermal oxidation (TO) and pack carburisation with limited oxygen diffusion (PCOD). Samples were tribological tested in a 0.9% NaCl solution under a contact load of 20 N to investigate the mechanical and electrochemical response of the surface treatments. The tests conducted show that a clear benefit can be obtained in terms of the overall material loss rate using both TO and PCOD. The TO and PCOD treatments generate very different surface structures: TO produces a rutile TiO2 surface film and the PCOD treatment produces a TiC network structure. Both treatments improve the load bearing capacity with the assistance of an oxygen diffusion zone (ODZ). When subjected to sliding contact in a 0.9% NaCl solution, the results show the PCOD-Ti produced the best overall results, with a material loss rate 7.5 times lower than untreated Ti and 2.4 times lower than TO-Ti. The improved wear rate of the PCOD-Ti is attributed to the TiC network structure. The TO-Ti suffers from rapid film failure and high friction. The reduced material loss rate (MLR) of the TO-Ti is attributed to the hard wearing ODZ.

Tribocorrosion response in biological environments of multilayer TaN films deposited by HPPMS

Abstract Biomedical implant failure arises mainly from the degradation caused by tribological processes occurring in the corrosive environment the human body represents, known as tribocorrosion. The material loss and metal ion release resulting from tribocorrosion processes compromise the biocompatibility of metallic implants. The deposition of protective coatings on metallic substrates is a promising solution to overcome this problem. Pure titanium (Ti-cp) is widely used as an implant material due to its excellent corrosion resistance and high biocompatibility. However, its mechanical properties must be improved in order to ensure a longer durability. For this purpose, TaN monolayer and multilayer coatings were deposited on medical grade Ti-cp to enhance its tribocorrosion performance in simulated body fluids. TaN coatings were deposited by recently developed High Power Pulsed Magnetron Sputtering (HPPMS) technique. HPPMS enables the deposition of extremely dense coatings with superior properties compared to the ones grown by conventional sputtering. Columnar-free TaN monolayer and multilayer films were developed exhibiting corrosion resistances in the MΩ range, one order of magnitude higher than for Ti-cp. Friction coefficient of Ti-cp was reduced from 0.58 to 0.25 while wear rate was considerably decreased. The determined material loss after tribocorrosion tests for Ti-cp was 0.4 mm3. It was reduced up to 1.55 × 10− 3 mm3 by the application of best-performing TaN multilayer film.

Influence of the carbon content on the corrosion and tribocorrosion performance of Ti-DLC coatings for biomedical alloys

Biomedical alloys are prone to suffer corrosion and wear phenomena coming from the hostile environment of the body and friction processes, respectively. Diamond-like carbon (DLC) coatings are known to be excellent candidates for using as protective coatings on biomedical alloys, not only due to their excellent tribological properties but also due to their chemical composition and stability. In this work, three Ti-DLC PVD coatings with different compositions were deposited on Ti6Al4V alloy and their corrosion and tribocorrosion responses were evaluated in simulated body fluid. Excellent tribocorrosion response has been found especially in case of coatings with high carbon content. Additionally significative reduction of friction and wear has been obtained in comparison to the substrate response.

Tribocorrosion response of the Ti6Al4V alloys commonly used in femoral stems

In prosthesis, tribochemical reactions occur at the stem/bone interface. When coupled with micro-motions it can lead to the loosening of the implant, osteolysis, release of metal ion and wear particles. The effect of these movements and the underlying mechanisms are quite unknown. This work investigates the tribocorrosion behavior of etched Ti6Al4V alloys under reciprocating sliding. Tests were performed in a phosphate buffer solution (PBS) containing proteins. A normal load of 1N and anodic potentials of −0.1 and +0.5V/SCE were applied. The destruction pathways of the top surface layers (adsorbed proteins, passive film) were studied. The results showed that the favorable/undesired effect of proteins in solution depends on the characteristics of the passive film under a mechanical stress.

Influence of fretting regimes on the tribocorrosion behaviour of Ti6Al4V in 0.9 wt.% sodium chloride solution

The effect of displacement amplitude, normal force and tribometer stiffness on the tribocorrosion response of a Ti6Al4V alloy in contact with a smooth alumina ball was investigated using a fretting corrosion rig equipped with an electrochemical cell. The roughness of the alloy plates was 0.6 μm, typical for the surface of hip joint stems. All experiments were carried out in 0.9 wt.% NaCl under anodic polarisation at a potential of 0.5 V versus the silver–silver chloride reference electrode, corresponding to the passive potential region. Anodic current, load, friction force and displacement amplitude were monitored in real time. Wear volume and surface morphology were evaluated at the end of fretting experiments. Results show that the prevailing fretting regime critically affects the overall system behaviour. Only fretting regimes involving slip led to measurable wear and to an enhancement of the anodic current. Previously developed tribocorrosion models for passivating metals were found to well describe the effect of normal force and displacement amplitude on the anodic current.