Towards Functional Silicon Nitride Coatings for Joint Replacements

Abstract

Silicon nitride (SiNx) coatings are currently under investigation as bearing surfaces for joint implants, due to their low wear rate and the good biocompatibility of both coatings and their potential wear debris. The aim of this study was to move further towards functional SiNx coatings by evaluating coatings deposited onto CoCrMo surfaces with a CrN interlayer, using different bias voltages and substrate rotations. Reactive direct current magnetron sputtering was used to coat CoCrMo discs with a CrN interlayer, followed by a SiNx top layer, which was deposited by reactive high-power impulse magnetron sputtering. The interlayer was deposited using negative bias voltages ranging between 100 and 900 V, and 1-fold or 3-fold substrate rotation. Scanning electron microscopy showed a dependence of coating morphology on substrate rotation. The N/Si ratio ranged from 1.10 to 1.25, as evaluated by X-ray photoelectron spectroscopy. Vertical scanning interferometry revealed that the coated, unpolished samples had a low average surface roughness between 16 and 33 nm. Rockwell indentations showed improved coating adhesion when a low bias voltage of 100 V was used to deposit the CrN interlayer. Wear tests performed in a reciprocating manner against Si3N4 balls showed specific wear rates lower than, or similar to that of CoCrMo. The study suggests that low negative bias voltages may contribute to a better performance of SiNx coatings in terms of adhesion. The low wear rates found in the current study support further development of silicon nitride-based coatings towards clinical application.

Do SiNx coatings bear the potential to reduce the risk of micromotion in modular taper junctions?

“…It was shown that those types of SiNx coatings have a higher coefficient of friction (163%) compared to uncoated samples during run-in phase, 47 notwithstanding Figure 7. Microscopic view onto the proximal coated male taper surface (Ti stem) after disassembly using laser microscopy.…”

The Effect of Coating Density on Functional Properties of SiNx Coated Implants

“…A previous study by Filho et al [38] evaluated the wear resistance of SiN x coatings deposited with 1- and 3-fold rotation (needed for future implant deposition) in a ball-on-disc system, in a hard-on-hard contact. While all coatings showed low wear rates against the Si 3 N 4 balls, it was found that the three-fold rotation reduced the coating density, which could influence the performance of the coating in its targeted application.…”

Microstructure and Antimicrobial Properties of Zr-Cu-Ti Thin-Film Metallic Glass Deposited Using High-Power Impulse Magnetron Sputtering

“…TiN coatings are also used extensively in the field of biomedicine, thanks to their resistance to wear and high biocompatibility. Therefore, TiN coatings are currently available on the market for knee replacements, particularly aimed at hypersensitive patients [ 40 ]. Chiang et al [ 41 ] reported on the relationship between the water contact angle on TFMG-coated surfaces and the presence of bacteria.…”