Metals 2 Flashcards
Oxide film
Oxidation/reduction reaction
Kinetic factor that control corrosion rate in biological aqueous solutions
Surface treatment reasons
- Corrosion resistance
- Blood compatibility
- Strength
- Biocompatibility
Blood compatibility
Adsorption of proteins
Effect of blood clotting
Gold results in the highest clotting effect
Surface Strength
Almost all cracks start at the surface
Done with Ion implantation
Ion Implantation
Raise surface strength and increases wear resistance
Surface biocompatibility
Deposition of hydroxyapatite (bone) or tricalcium phosphate
Done with plasma spraying
Sintering
Making objects from powders by heating the powder material below their melting point until they adhere to one another
Ti properties
Light weight
Excellent corrosion resistance
MOST biocompatibility
Soft (low wear and friction properties)
Ti alloys
cpTi (4 grades, impuritites)
Ti6Al4V
cpTI
More Oxygen equals greater strength
Ti crystallographic forms
Alpha (low temp)
Beta (high temp)
Ti alpha alloys
Al, gallium, or tin NOT heat-treatable Weldable Good creep, NO ductile-brittle transform Low temp applications (not biomedical)
Ti beta alloys
Heat treatable and cold formable
Undergoes ductile-brittle transform
NOT suitable for low temp apps
Isomorphous and Eutectoid
Ti alpha-beta alloys
Ti6Al4V Good formability Heat treatable High tensile strength Not weldable
Reasons to use Stainless steel
Easy to obtain Inexpensive Highly Machinable Low failure rate NOT interchangeable parts
SS characteristics
Iron-based with Cr
SS alloys
Martensitic
Ferritic
Austenitic
Duplex
Martensitic SS
Heat treatment
Surgical and dental instruments
Low Cr
Ferritic SS
NO Heat treatment
Handles for instruments
Low-mid Cr
Austenitic SS
Med-mid Cr
NO heat treatment
Medical implants and devises
ex. 316L
316L SS
Cold-worked
Stents, implants, fracter fixers
Duplex SS
Equally ferrite and austenite
NOT used
Cobalt-chromium properties
High wear resistance (articulation)
Very dense and heavy
95% of knee implants
CoCr Alloys
CoCrMo is hardest, strongest and most fatigue resistant for biomedical apps
cold working
