Significant Improvement in Mechanical Properties of Biomedical Co-Cr-Mo Alloys with Combination of N Addition and Cr-Enrichment

Lee, Sang Hak; Nomura, Naoyuki; Chiba, Akihiko

doi:10.2320/matertrans.mra2007220

Cited by 110 publications

(49 citation statements)

References 18 publications

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“…The solubility of N in Co-Cr-Mo alloys increases with increasing Cr content from 29 to 34 mass%. 1) N contributes to the suppression of the martensite and σ phase formation. The high Cr and N content in Co-Cr-Mo alloy results in a signi cant improvement in mechanical properties such as yield strength, tensile strength, and elongation, and the improvement cannot be achieved only with high Cr in the alloy.…”

Section: Introductionmentioning

confidence: 99%

Surface Composition and Corrosion Resistance of Co-Cr Alloys Containing High Chromium

et al. 2016

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Air-formed surface oxide lms on four types of Co-Cr-alloys were characterized using X-ray photoelectron spectroscopy (XPS) and ve types of Co-Cr alloys were anodically polarized, to identify the effects of the addition of N, Mo, and W to Co-Cr alloys containing high Cr on the surface composition and corrosion resistance. Co-20Cr-15W-10Ni (ASTM F90), Co-30Cr-6Mo, Co-33Cr-5Mo-0.3N, and Co-33Cr-9W-0.3N were employed for XPS and the above four alloys and another Co-30Cr-6Mo (ASTM F75) were employed for anodic polarization. . Cr and Mo are enriched and Co and Ni are depleted in the surface oxide lm. W was enriched in the case of Co-20Cr-15W-10Ni but depleted in the case of Co-33Cr-9W-0.3N. On the other hand, Cr, Mo, W and Ni were enriched and Co was depleted in the substrate alloy just under the surface oxide lm in the polished alloy. During rapid formation of the surface oxide lm, Cr was preferentially oxidized and the oxidation of Co and Ni delayed, according to the oxidation and reduction potentials of these elements. The Co-Cr alloys essentially have high localized corrosion resistance that is not easily affected by a small change of composition. Co-33Cr-5Mo-0.3N shows higher corrosion resistance compare than conventional Co-Cr alloys.

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Section: Introductionmentioning

confidence: 99%

Surface Composition and Corrosion Resistance of Co-Cr Alloys Containing High Chromium

et al. 2016

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“…To improve the strength and elongation of the alloys, the addition of nitrogen (N) was effective because N stabilizes the phase and decreases the athermal " phase in the alloy. 6) For the fabrication of N-added Co-Cr-Mo alloys, Co-Cr-Mo was melted with the Cr 2 N powders. 6) However, the yield ratio of N was low owing to the vaporization of N 2 .…”

Section: Introductionmentioning

confidence: 99%

“…6) For the fabrication of N-added Co-Cr-Mo alloys, Co-Cr-Mo was melted with the Cr 2 N powders. 6) However, the yield ratio of N was low owing to the vaporization of N 2 . Sato et al 7) controlled the N content in Co-29Cr-6Mo compacts by changing the mixture ratio of Ar and N 2 gases.…”

Section: Introductionmentioning

confidence: 99%

Microstructures of Zr-Added Co-Cr-Mo Alloy Compacts Fabricated with a Metal Injection Molding Process and Their Metal Release in 1 mass% Lactic Acid

et al. 2010

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The microstructures of Zr-added Co-29Cr-6Mo alloy compacts fabricated with a metal injection molding (MIM) process and their metal release from the compacts immersed in 1% lactic acid were investigated for medical applications. The relationship between the microstructure and amount of Co released from the compacts is discussed phenomenologically. The relative density of the Co-29Cr-6Mo compacts increased when Zr was added to the powder with amounts of 0.03 and 0.1 mass% and sintered in Ar or N 2 . The amounts of Co released from the compacts containing 0.03 and 0.1 mass% Zr sintered in Ar or N 2 were smaller than those from the other compacts. Therefore, the addition of Zr to the Co29Cr-6Mo powders enhanced the sintering of the compacts and decreased the porosity in the resultant products, leading to the suppression of the Co release from the compacts. When the Zr-added Co-29Cr-6Mo alloy powders were sintered in N 2 , the relative density of the compacts was smaller than that of those sintered in Ar. The powders were nitrided during sintering in N 2 , and the nitrides disturbed the densification during sintering. In addition, a lamellar structure was formed in the Co-29Cr-6Mo and Co-29Cr-6Mo-0.5Zr compacts. The amount of Co released from these compacts was larger than that released from the other compacts because local corrosion occurred at the interface between the different phases in these compacts during immersion in 1% lactic acid. In the MIM process, a small addition of Zr (less than 0.1 mass%) to the Co-29Cr-6Mo alloy is effective for densification during sintering and suppression of the Co release from the compacts.

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“…The high strength which has been achieved opens the possibility for reduction of implant sizes where limited anatomical space is often an issue, for example, coronary stents with finer meshes (Yang, 2010). In CoCr alloys system, maximizing C content to its upper limit and addition of Zr and N with optimal precipitation hardening permit the formation of fine and distributed carbides and the suppression of -phase which in turn improves the wear resistance of cast CoCr alloy (Lee, 2008). Contrary, for wrought CoCr alloys, addition of N and suppression of carbides and intermetallics results into the desired better workability (Chiba, 2009).…”

Section: New Generation Of Metallic Biomaterialsmentioning

confidence: 99%

Metals for Biomedical Applications

Hermawan¹,

Ramdan²,

Djuansjah³

2011

Biomedical Engineering - From Theory to Applications

176

125

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Biomedical Engineering -From Theory to Applications 412 visible under X-ray imaging. Most of artificial implants are subjected to loads, either static or repetitive, and this condition requires an excellent combination of strength and ductility. This is the superior characteristic of metals over polymers and ceramics. Specific requirements of metals depend on the specific implant applications. Stents and stent grafts are implanted to open stenotic blood vessels; therefore, it requires plasticity for expansion and rigidity to maintain dilatation. For orthopaedic implants, metals are required to have excellent toughness, elasticity, rigidity, strength and resistance to fracture. For total joint replacement, metals are needed to be wear resistance; therefore debris formation from friction can be avoided. Dental restoration requires strong and rigid metals and even the shape memory effect for better results. In overall, the use of biomaterials in clinical practice should be approved by an authoritative body such as the FDA (United States Food and Drug Administration). The proposed biomaterial will be either granted Premarket Approval (PMA) if substantially equivalent to o n e u s e d b e f o r e F D A l e g i s l a t i o n o f 1 9 7 6 , o r h a s t o g o t h r o u g h a s e r i e s o f g u i d e d biocompatibility assessment. Common metals used for biomedical devicesUp to now, the three most used metals for implants are stainless steel, CoCr alloys and Ti alloys. The first stainless steel used for implants contains ~18wt% Cr and ~8wt% Ni makes it stronger than the steel and more resistant to corrosion. Further addition of molybdenum (Mo) has improved its corrosion resistance, known as type 316 stainless steel. Afterwards, the carbon (C) content has been reduced from 0.08 to 0.03 wt% which improved its corrosion resistance to chloride solution, and named as 316L. Titanium is featured by its light weight. Its density is only 4.5g/cm 3 compared to 7.9g/cm 3 for 316 stainless steel and 8.3g/cm 3 for cast CoCrMo alloys (Brandes and Brook, 1992). Ti and its alloys, i.e. Ti6Al4V are known for their excellent tensile strength and pitting corrosion resistance. Titanium alloyed with Ni, i.e. Nitinol, forms alloys having shape memory effect which makes them suitable in various applications such as dental restoration wiring. In dentistry, precious metals and alloys often used are Au, Ag, Pt and their alloys. They possess good castability, ductility and resistance to corrosion. Included into dental alloys are AuAgCu system, AuAgCu with the addition of Zn and Sn known as dental solder, and AuPtPd system used for porcelain-fused-to-metal for teeth repairs. CoCr alloys have been utilised for many decades in making artificial joints. They are generally known for their excellent wear resistance. Especially the wrought CoNiCrMo alloy has been used for making heavily loaded joints such as ankle implants (Figure 1). Other metals used for implants include tantalum (Ta), amorphous alloys and biodegradable metals. Tantalum which has excell...

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Significant Improvement in Mechanical Properties of Biomedical Co-Cr-Mo Alloys with Combination of N Addition and Cr-Enrichment

Cited by 110 publications

References 18 publications

Surface Composition and Corrosion Resistance of Co-Cr Alloys Containing High Chromium

Surface Composition and Corrosion Resistance of Co-Cr Alloys Containing High Chromium

Microstructures of Zr-Added Co-Cr-Mo Alloy Compacts Fabricated with a Metal Injection Molding Process and Their Metal Release in 1 mass% Lactic Acid

Metals for Biomedical Applications

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