Nickel‐free high‐nitrogen austenitic steel outperforms CoCrMo alloy regarding tribocorrosion in simulated inflammatory synovial fluids

Abstract

CoCrMo alloys are well‐established biomaterials used for orthopedic joint replacement implants. However, such alloys have been associated with clinical problems related to wear and corrosion. A new generation of austenitic high‐nitrogen steels (AHNSs) has been developed for biomedical applications. Here, we have addressed influences of hyaluronic acid, combined with inflammatory (oxidizing) conditions, on tribocorrosion of the high‐nitrogen FeCrMnMoN0.9 steel (DIN/EN X13CrMnMoN18‐14‐3, 1.4452), and of the low carbon CoCrMo0.03 alloy (ISO 5832‐12). We aimed to elucidate critical and clinically relevant conditions affecting the implant's performance in certain orthopedic applications. Tribocorrosion tests were conducted in triplicate, with discs under reciprocating sliding wear against a ceramic ball. Different lubricants were prepared from standardized bovine serum solution (ISO 14242‐1), with variable additions of hyaluronic acid (HA) and hydrogen peroxide (H2O2). Test conditions were: 37°C, 86,400 cycles, 37 N load (20–40 MPa after run‐in phase). Volumetric wear was quantified; surfaces were evaluated by electrochemical parameters and microscopy/spectroscopy analyses (SEM/EDS). Factorial analysis of variance tests was conducted to examine the effects of HA, H2O2, and test material on wear‐ and corrosion‐related dependent variables. Tribocorrosion performances of CoCrMo0.03 and FeCrMnMoN0.9 were comparable in fluids without H2O2. With higher H2O2 concentrations, tribocorrosion increased for CoCrMo0.03, while this was not the case for FeCrMnMoN0.9. HA significantly enhanced wear of CoCrMo0.03 in the absence of H2O2, while it mitigated the tribocorrosive action of 3 mM H2O2; HA had no impact on FeCrMnMoN0.9. These results indicate a favorable performance of FeCrMnMoN0.9 compared to CoCrMo0.03, and encourage further research on AHNS for certain orthopedic applications.

Performance of Austenitic High-Nitrogen Steels under Gross Slip Fretting Corrosion in Bovine Serum

“…Thus, the AHNSs appear to show a better behavior than the Co alloy if the submechanisms of the tribochemical reactions, like tribocorrosion and tribo-oxidation, markedly influence the wear behavior. Already in an earlier investigation under more inflammatory conditions, we saw the advantage of FeCN0.9 against CoC0.03 for its better tribochemical properties [54]. This is also indicated by the smaller ∆OCP of the ZTA/AHNS and AHNS/AHNS couples (Figure 4).…”

“…From the ∆OCP, we can only read that the smaller, the less ions are released and, therefore, the better. In a rough approximation as to this criterion, we could write that AHNSs would outperform the Co alloy [54] and that Ti6Al4V would be the worst if run against an alumina-based ceramic [34]. But, if FL-Ti6Al4V is run against the AHNS (Table 6), the ∆OCP values do not follow that trend.…”

“…In earlier studies, it has been shown by both in vitro and in vivo studies that Co-and Ni-free austenitic high-nitrogen steels (AHNSs) have adequate mechanical and chemical properties for biotribological applications and are biocompati-ble [47][48][49][50][51][52][53]. In particular, it was found that these steels have a better repassivation behavior than CoCrMo in electro-impedance spectroscopy experiments, as well as under reciprocating sliding wear in contact with Al 2 O 3 [54]. Thus, AHNSs could, in principle, replace CoCrMo in some applications.…”

Interactions between hyaluronic acid and CoCrMo alloy surface in simulated synovial fluids

“…The higher current density values measured in DPBS + NCS + HA, compared to DPBS + HA, are likely due to limited surface adsorption of phosphates, which reduce the corrosion rate of the alloy, caused by the presence of proteins [33]. The pH increase between the beginning and the end of the test, measured in the bulk solution when proteins were present in the solution, has been observed elsewhere and appeared to be independent of the test material, specific fluid composition, and protocol [14, 34–36]; it might be related to spontaneous degradation reactions of asparagine, a derived form of the amino acid aspartic acid, leading to deamination of its residues via the succinimide intermediate with the release of ammonia, making the solution more basic [37]. We would, therefore, expect the surface pH behaviour in DPBS + NCS + HA to be similar to the one measured in DPBS + HA.…”

Study of Effect of Nickel Content on Tribocorrosion Behaviour of Nickel–Aluminium–Bronzes (NABs)

“…Tribocorrosion involves the tribological interactions between the mechanically induced interactions with electrochemical processes, causing the materials to corrode at substantially higher rates than those experienced under static or quiescent conditions, enhancing wear processes due to corrosion [1]. Numerous studies on the tribocorrosion behaviour of metallic materials related to biomedical applications, such as Co-Cr and titanium alloy, have been published over the last 20 years [2][3][4][5][6][7][8][9]. In Jiang et al's [10] tribocorrosion modelling proposal for marine alloys, the microstructure, presence of multiple wear mechanisms, localised corrosion, and complex film formation are the key factors to understand this phenomenon, as confirmed by Landolt [11] regarding the role of the passive layer.…”