The Influence of Plasma-Based Nitriding and Oxidizing Treatments on the Mechanical and Corrosion Properties of CoCrMo Biomedical Alloy

Abstract

Plasma-based nitriding and/or oxidizing treatments were applied to CoCrMo alloy to improve its surface mechanical properties and corrosion resistance for biomedical applications. Three treatments were performed. A set of CoCrMo samples has been subjected to nitriding at moderate temperatures (~400°C). A second set of CoCrMo samples was oxidized at 395°C in pure O 2 . The last set of CoCrMo samples was nitrided and subsequently oxidized under the experimental conditions of previous sets (double treatment). The microstructure and morphology of the layers formed on the CoCrMo alloy were investigated by X-ray diffraction, Atomic Force Microscopy, and Scanning Electron Microscopy. In addition, nitrogen and oxygen profiles were determined by Glow Discharge Optical Emission Spectroscopy, Rutherford Backscattering Spectroscopy, Energy-Dispersive X-ray, and Nuclear Reaction Analysis. Significant improvement of the Vickers hardness of the CoCrMo samples after plasma nitriding was observed due to the supersaturated nitrogen solution and the formation of an expanded FCC c N phase and CrN precipitates. In the case of the oxidized samples, Vickers hardness improvement was minimal. The corrosion behavior of the samples was investigated in simulated body fluid (0.9 pct NaCl solution at 37°C) using electrochemical techniques (potentiodynamic polarization and cyclic voltammetry). The concentration of metal ions released from the CoCrMo surfaces was determined by Instrumental Neutron Activation Analysis. The experimental results clearly indicate that the CoCrMo surface subjected to the double surface treatment consisting in plasma nitriding and plasma oxidizing exhibited lower deterioration and better resistance to corrosion compared to the nitrided, oxidized, and untreated samples. This enhancement is believed to be due to the formation of a thicker and more stable layer.

Anisotropic microstructure and mechanical properties of additively manufactured Co–Cr–Mo alloy using selective electron beam melting for orthopedic implants

“…However, such as the artificial joint, bio-tribological properties of Co-Cr-Mo alloys also affect the lifespan of the implant [39][40][41] . Cawley et al [42] found that more carbides could improve the surface hardness of Co-Cr-Mo alloys, which could reduce wear in human body fluids.…”

Ground-State Atomic Nitrogen Measurements using fs-TALIF in High-Pressure NRP Discharges

“…The two-photon absorption scheme used in the current work involves the excitation of the 3p 4 S3/2 level ( λ = 2 ×206.6 nm) with the subsequent fluorescence collection taking place from the radiative decay to the 3s 4 P triplet state around 745 nm. If the fluorescence comes exclusively from the two-photon laser excited state, it can be used to directly probe the ground population of atomic nitrogen (2p 3 In principle, at the high laser fluences that characterizes the femtosecond sources of excitation, the model suggests that it is possible to perform fluorescence measurements that are insensitive to quenching. This is demonstrated in Fig.…”

“…tomic nitrogen obtained by efficient dissociation in a nanosecond pulsed repetitively pulsed (NRP) discharge can be useful for many industrial applications such as the enhancement of nitridation processes 1 , the synthesis of novel nanomaterials 2 or biomedical treatment 3,4 . Additionally, understanding the kinetics of atomic nitrogen production at high-pressure conditions (above 1 bar) can be used to better understand the plasma influence on NOx generation in plasma-assisted combustion applications 5,6 .…”

“…However, this technique cannot be used to determine the concentration of N( 4 S) during the discharge. 1 Postdoctoral Fellow, ciprian.dumitrache@centralesupelec.fr, AIAA Member 2 PhD Student, arnaud.gallant@centralesupelec.fr 3 Professor, gabi-daniel.stancu@centralesupelec.fr 4 Professor, chirstophe.laux@centralesupelec.fr, AIAA Associate Fellow The main goal of this work is to present a new diagnostic technique, based on femtosecond two-photon absorption laser-induced fluorescence (fs-TALIF), that enables spatially and temporally resolved measurements of ground-state population of atomic nitrogen in an NRP discharge at high pressures (p ≥ 1 bar). The first nitrogen TALIF experiment was performed by Bischel et al 10 inside a flow discharge in which atomic nitrogen was obtained by N2 dissociation in a He+SF6 buffer gas mixture at ~10 Torr.…”

Femtosecond Two-Photon Absorption Laser Induced Fluorescence (fs-TALIF) Imaging of Atomic Nitrogen in Nanosecond Repetitive Discharges

“…fficient production of large amounts of nitrogen atoms is of importance for many industrial applications such as the enhancement of nitridation processes 1 , the synthesis of novel nanomaterials 2 or biomedical treatments 3,4 . Moreover, it is also important to understand the high-pressure kinetic pathways that lead to atomic nitrogen production in plasma-assisted combustion in order to evaluate the plasma influence on NOx generation 5,6 .…”