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

Luimar Correa Filho,Cecilia Persson,Alejandro López,Susann Schmidt,Håkan Engqvist,Klaus Leifer,Hans Högberg,Mathilde Cogrel

doi:10.3390/ma12203370

Luimar Correa Filho, Cecilia Persson + Show 6 more

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https://doi.org/10.3390/ma12203370

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Abstract

Ceramic coatings may be applied onto metallic components of joint replacements for improved wear and corrosion resistance as well as enhanced biocompatibility, especially for metal-sensitive patients. Silicon nitride (SiNx) coatings have recently been developed for this purpose. To achieve a high coating density, necessary to secure a long-term performance, is however challenging, especially for sputter deposited SiNx coatings, since these coatings are insulating. This study investigates the time-dependent performance of sputter-deposited SiNx based coatings for joint applications. SiNx coatings with a thickness in the range of 4.3–6.0 µm were deposited by reactive high power impulse magnetron sputtering onto flat discs as well as hip heads made of CoCrMo. SiNx compositional analysis by X-ray photoelectron spectroscopy showed N/Si ratios between 0.8 and 1.0. Immersion of the flat disks in fetal bovine serum solution over time as well as short-term wear tests against ultra-high molecular weight polyethylene (UHMWPE) discs showed that a high coating density is required to inhibit tribocorrosion. Coatings that performed best in terms of chemical stability were deposited using a higher target power and process heating.

Highlights

In order to reduce metal ion release, while maintaining or improving the wear resistance, different ceramic coatings have been evaluated for the metallic parts of joint implants, and are used in knee implants in sensitive patients [1,2]
A reactive high power impulse magnetron sputtering process was developed for the deposition of a CrN interlayer, followed by a top layer of SiNx or SiCN on CoCrMo flat discs and CoCrMo heads for hip implants, based on an earlier study [42]
Samples with one-fold rotation presented higher silicon and nitrogen contents, lower oxygen and carbon contents, and slightly higher N/Si ratios compared to three-fold rotation coatings

Summary

Introduction

In order to reduce metal ion release, while maintaining or improving the wear resistance, different ceramic coatings have been evaluated for the metallic parts of joint implants, and are used in knee implants in sensitive patients [1,2]. Alumina coatings, deposited with an Al3 Ti interlayer, have been found to present a higher hardness similar to that demonstrated by bulk alumina ceramic, and the use of interlayers can improve crack resistance and adhesion to the substrate [3,4,5]. CrN and CrCN have shown reduced wear compared to some DLC coatings, and when sliding against polyethylene the result was similar to that of a commonly used bulk ceramic [6,7,8,9,10]. TiN has a well-known high wear resistance and with demonstrated reduced metal ion release compared to CoCr [3,11,12,13,14]. DLC is a coating with high hardness and a low coefficient of friction due to self-lubricating characteristics that has been found to give a reduced

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