Abstract
Silicon nitride (SiNx) coatings are promising for joint replacement applications due to their high wear resistance and biocompatibility. For such coatings, a higher nitrogen content, obtained through an increased nitrogen gas supply, has been found to be beneficial in terms of a decreased dissolution rate of the coatings. The substrate temperature has also been found to affect the composition as well as the microstructure of similar coatings. The aim of this study was to investigate the effect of the substrate temperature and nitrogen flow on the coating composition, microstructure and mechanical properties. SiNx coatings were deposited onto CoCrMo discs using reactive high power impulse magnetron sputtering. During deposition, the substrate temperatures were set to 200 °C, 350 °C or 430 °C, with nitrogen-to-argon flow ratios of 0.06, 0.17 or 0.30. Scanning and transmission electron spectroscopy revealed that the coatings were homogenous and amorphous. The coatings displayed a nitrogen content of 23–48 at.% (X-ray photoelectron spectroscopy). The surface roughness was similar to uncoated CoCrMo (p = 0.25) (vertical scanning interferometry). The hardness and Young’s modulus, as determined from nanoindentation, scaled with the nitrogen content of the coatings, with the hardness ranging from 12 ± 1 GPa to 26 ± 2 GPa and the Young’s moduli ranging from 173 ± 8 GPa to 293 ± 18 GPa, when the nitrogen content increased from 23% to 48%. The low surface roughness and high nano-hardness are promising for applications exposed to wear, such as joint implants.
Highlights
IntroductionJoint replacement surgery is a common procedure that can improve the quality of life for patients suffering from, e.g., arthrosis: in Sweden alone, 16,566 primary total hip arthroplasties (THA) and
Joint replacement surgery is a common procedure that can improve the quality of life for patients suffering from, e.g., arthrosis: in Sweden alone, 16,566 primary total hip arthroplasties (THA) and13,000 primary total knee arthroplasties (TKA) were performed in 2014 [1,2]
When the substrate temperature was increased to 350 ◦ C, similar N
Summary
Joint replacement surgery is a common procedure that can improve the quality of life for patients suffering from, e.g., arthrosis: in Sweden alone, 16,566 primary total hip arthroplasties (THA) and. 13,000 primary total knee arthroplasties (TKA) were performed in 2014 [1,2] The incidence of both THA and TKA is predicted to increase [3]. In 2007, silicon nitride was introduced as a potential femoral head material for hip joint implants [12]. It is considered a suitable candidate for joint implant coatings because of its wear resistance [13,14] and dissolution into non-toxic ions in aqueous solutions [15,16,17,18]. A high solubility of the wear particles (decreasing the risk for third-body wear or negative biological reactions), but a low solubility of the coating itself (making it last longer) would be optimal
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