The Tribocorrosion Behaviour of Ti-6Al-4 V Alloy: The Role of Both Normal Force and Electrochemical Potential

Abstract

The tribocorrosion behaviour of Ti-6Al-4 V exposed to phosphate buffered saline was investigated under a range of normal forces in both cathodic and anodic regions to provide a basis for properly deriving the tribological constants of this alloy. To achieve this, a new customised tribotester was designed and manufactured to rub the Ti-6Al-4 V disks against zirconia balls. The tests were conducted at a sliding frequency of 1 Hz and a sliding distance of 4.8 mm under various normal forces and potentials as 17.5, 10.8, 6, 3.5 N, and − 1.2, − 0.6, 0, 0.4, 0.8 V/VAg/AgCl, respectively. The damaged surfaces were characterised by scanning electron microscopy and energy-dispersive X-ray spectroscopy, profilometer, and micro-hardness tester. The post analyses confirmed the appearance of some minor cracks together with third-body wear particles. No significant changes in the hardness were detected after the tribocorrosion tests. The results of profilometry and electrochemical current indicated that in the anodic region the chemical losses accounted for a significant proportion (up to 36%) of the total loss. The proportional chemical loss increased with the potential; however, neither direct nor reverse relationship was found with the normal force. Overall, in the anodic domain, the material loss increased with the potential level due to the formation of oxide layer which may induce more shear cutting. In the cathodic domain, hydrogen embrittlement changed the properties of the interface and thus, the amount of material loss. Both the mechanical and chemical wear were described by an existing tribocorrosion theory; thereby, the theory was equipped with its tribocorrosive constants for future analyses on the tribocorrosion of this alloy extensively used in various applications including biomedical implants.

An Overview of the Stability and Fretting Corrosion of Microgrooved Necks in the Taper Junction of Hip Implants

“…The basic data for such a modeling procedure can be obtained by fundamental tribocorrosion studies in the ball-on-disc configuration. The role of mechanical and electrochemical reactions in the total tribocorrosion loss changes with various parameters such as the imposed potential [ 48 , 49 ], normal force (and, thus, contact pressure) [ 50 , 51 ], sliding distance and its frequency [ 52 , 53 , 54 ], material couple in contact [ 55 , 56 , 57 , 58 ], and the solution type and its acidity [ 59 , 60 , 61 ]. However, the design parameters of head–neck junctions including taper angle mismatch, head size, trunnion geometry, material couples in contact, and the solution acidity, together with the presence of proteins, could affect the tribological characteristics of the system, the governing potential, and the degree of mechanical and electrochemical damage processes.…”

Assessing the wear degradation of tungsten in acidic solutions using a lubricated tribocorrosion model

“…Many studies have shown the important role played by the normal force on mechanical wear accelerated corrosion, and fluid lubrication in the tribocorrosion of passive metals. 16,17,27,31 Figure 3 shows the effect of normal force on the mechanical, chemical, and total wear rates of tungsten in tribocorrosion according to the model. Both of the mechanical and chemical wear rates increase at higher normal force, while it is interesting to see that the mechanical and chemical wear curves intersect at the normal force of approximately 60 N. Specifically, the effect of normal force on the chemical wear rate is less and less pronounced with the increase of the normal force while the effect of normal force on the mechanical wear rate keeps enhancing at higher normal force.…”

“…the clear dependence of anodic current on the applied potential which is consistent with the observations found in the tribocorrosion of other passive metals. 16,17,25 However, a reliable model to predict the influence of these parameters on the material removal of tungsten in tribocorrosion is not yet developed.…”

“…13,14 The tribocorrosion mechanism of the commonly used passive metals (e.g. stainless steels, CoCr alloys, Ti alloys, and Al alloys) has been intensively studied using tribo-electrochemical techniques, 15–18 and models have been developed to describe the material loss in the tribocorrosion degradation of passive metals. 19 However, only a few studies 13,20–22 reported the tribocorrosion behavior of tungsten in typical polishing solutions.…”

The Role of the Assembly Force in the Tribocorrosion Behaviour of Hip Implant Head-Neck Junctions: An Adaptive Finite Element Approach

“…To further improve the estimation of the material loss during the operation of the hip implant, the tribocorrosion (fretting corrosion) phenomenon at the head-neck junction requires investigation. To achieve this, both the mechanical wear and electrochemical corrosion need to be modelled simultaneously [ 17 ]. Modelling tribocorrosion has been a major challenge for researchers, due to its complexity [ 18 ].…”