Mechanical load assisted dissolution response of biomedical cobalt–chromium and titanium metallic alloys: Influence of in-plane stress and chemical environment

Abstract

a b s t r a c tMechanical load-assisted dissolution is identified as one of the key mechanisms governing material removal in fretting and crevice corrosion of biomedical implants. In the current study, material removal on a stressed surface of cobalt-chromium-molybdenum (CoCr) and titanium (Ti-64) alloys subjected to single asperity contact is investigated in order to identify the influence of contact loads and in-plane stress state on surface damage mechanisms. The experiments were conducted in ambient as well as three different aqueous environments -phosphate buffered saline (PBS) at pH 7.4, PBS at pH 4.1 and high chloride solutions at pH 4.0. The tip of an atomic force microscope is used as a well-characterized "asperity" to apply controlled contact forces and mechanically stimulate the loaded specimen surface in different aqueous environments from passivating to corroding. The volume of the material removed is measured to determine the influence of contact loads, in-plane stresses and the environment on the material dissolution rate. Experimental results indicate that surface damage is initiated at all the contact loads studied and as expected in a wear situation, removal rate increases with increase in contact loads. For both alloys, removal rates display a complex dependence on residual stresses and the environment. In a passivating environment, the material removal rate is linearly dependent on the stress state such that surface damage is accelerated under compressive stresses and suppressed under tensile stresses. In a corrosive environment, the dissolution rate demonstrates a quadratic dependence on stress, with both compressive and tensile stresses accelerating material dissolution. The material removal rates are found to be consistently larger for CoCr in comparison to Ti64 surfaces under the same mechanical and electrochemical stimuli, despite the higher hardness of CoCr surfaces.

Differences in indentation and wear behaviors between the two sides of thermally tempered soda lime silica glass

“…These subtle differences in local structures may not affect the mechanical scratch in dry condition because the stochastic nature of abrasion is already severe; but they may be manifested as an increase in SD during the mechanochemical process in high humidity condition because such reactions are very sensitive to local strains in chemical bonds 53,54,55,56 . Similar observations were reported for ion‐exchanged aluminosilicate glass 21,57 and metals and alloys as well 58–60 …”

Sliding Corrosion Fatigue of Metallic Joint Implants: A Comparative Study of CoCrMo and Ti6Al4V in Simulated Synovial Environments

“…However, due to their superior mechanical and biochemical performance, Ti and CoCr alloys are continually used in current joint implant manufacturing. The previous investigation of tribocorrosion of metallic implants indicates that the CoCr surface showed more wear rate than the Ti alloy surface under the same mechanical and electrochemical stimuli, despite the greater hardness of the Co-Cr surface compared to that of the Ti alloy surface [33][34][35][36]. Previous studies agreed with the retrieval studies of hip replacements: at the CoCr-Ti junction, the harder CoCr surface showed faster wear behavior than the counter Ti surface [12,37].…”

Torsional fretting corrosion behaviours of Ti6Al4V alloys in Hank’s simulated body fluid

“…Many scholars have studied the fretting corrosion behaviours [6][7][8][9][10][11] and tribo-electrochemical characterisation [12][13][14][15][16] of metallic artificial joint materials (especially Titanium alloy) in different solutions intended for biomaterial applications. Numerous scientists agree that fretting corrosion is a major factor in the failure of artificial joints [17][18][19].…”