Cobalt Alloys.pdf

COBALT ALLOYS AS BIOMATERIAL-MUKESH SUNDARARAJAN

1. Cobalt-Based
Alloys
MUKESH
SUNDARARAJAN

2. INTRODUCTION
•Cobalt-Based alloys are materials whose cobalt-basis is
alloyed with elements such as chromium, tungsten, nickel
and iron. Along with nickel-based alloys, they are used in
challenging environments including high temperatures
and acids.

3. PROPERTIESOFCOBALT:
➢Physicalproperties:
•Alustrous,silvery-bluemetal.Itismagnetic.
•Density8.9g.cm
-3at20°C
•Meltingpoint1495 °C
•Boilingpoint2927°C
•Itisabrittle,hardmetal.
•Ithas ametallicpermeabilityofabout
twothirdsthatofiron.
•Ithashexagonalstructure.

4. ➢CHEMICALPROPERTIES:
•Cobaltisamoderatelyreactiveelement.
•Itdoesnotreactwithwateratroom
temperatures.
•Itreactswithmostacidstoproducehydrogengas.
•Itcombinesslowlywithoxygenintheair,butdoesnotcatchfireand
burnunlessitisinapowderform.
•Itwillburnbrightlywhenincontactwithair.

5. APPLICATIONSOFCOBALT:
•Paintpigments.
•-Nickel-basesuperalloys.
•-Cementedcarbidesand toolsteels.
•-Magneticmaterials.
•-Artificialg-raysources.
•-Cobalt isalsoused to makealloysfor jet enginesandgasturbines.
•-Cobalt-60,a radioactiveisotopeof cobalt,isan importantsourceofgammarays
and is usedto treatsomeformsofcancerandas a medicaltracer.
•Cobalt metal is sometimes used in electroplating because of itsattractive
appearance,hardnessandresistancetocorrosion.

6. ALLOYSOFCOBALT
❑Wearresistancealloys
❑HeatResistanceAlloys
❑CorrosionResistanceAlloys

7. 1.WEARRESISTANCEALLOYS:
•Alloysarethosethataremadetoresistabrasivewear,
slidingwear,anderosivewear.
•Theyconsistmostlyofcobaltandchromiumbutmayalso
containtungstenormolybdenumandasmallamount
ofcarbon.

8. •ChemicalcompositionofStellitealloys isapproximately:
•Cr~25-30%
•Mo= 1%max
•W=2-15%
•C=0.25-3.3%
•Fe=3%max
•NI=3%max
•Si=2%max
•Mn=1%max
•Co=restofbalance

9. 2.HEATRESISTANCEALLOYS
•Althoughtheyarenotaswidelyusedasnickelbased
high-temperaturealloys.
•Theyplayaroleintemperaturesabovenickel’s
deteriorationpointandinapplicationswhere
sulfidationresistanceisimportant.

10. •Ingeneral,cobalt-basehigh-temperaturealloyshavethe
followingchemicalcomposition:
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Cr=20-23%
W=7-15%
Ni=10-22%
Fe=3%max
C=0.1-0.6%
Co=restof balance.

11. 3.CORROSIONRESISTANCEALLOYS
•Alloysare thosethat aredesignedto resistaqueous
corrosion.
•They are limited in their corrosion resistance in
comparison to nickel-chromium-molybdenum
alloys.
•However, several low-carbon, wrought cobalt-
nickel-chromium-molybdenumalloysexistto
satisfytheneedfora corrosionresistantcobalt
basealloy.

12. •Chemicalcompositionofthesealloysis:
•▶
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Cr=20-25%
W=2%
Mo=5-10%
Ni=9-35%
Fe = 3% max
C = 0.8% max
N=0.1% max
Co=restofbalance.

13. Cobalt (Co) alloys have been used for over seven decades in a wide range of
medical devices, including, but not limited to, hip and knee implants, surgical
tools, and vascular stents, dueto their favorable biocompatibility, durability,
and mechanical properties.
•Cobalt-based alloys and austenitic stainless steelsfor prostheses
and trauma implants
•High performance stainless steelsfor surgical instruments (blades,
scalpels, etc.) and medical devices (stamples, needles, etc.).
•High-corrosion-resistant cobalt-chromium alloys are used for fabricating
dental restorations such as all-metal crowns or bridges, denture
frameworks or implant abutments.
Medical applicationsof Cobaltalloys

15. THANK YOU