Metals Flashcards
CoCr
High wear resistance
Polishing
Does not interact with bone
Ti
Too soft for articulating
Good for bone
General Characteristics
4
High corrosion resistance
Biocompatibility
High wear resistance
Mechanical properties
Oxide layer
3
Key to biocompatibility
Responsible for corrosion resistance
Assist with osseointegration
Biocompatibility
ability to minimize adverse host reactions
High wear resistance
Necessary to prevent leechables
Mechanical properties
Static and fatigue
Stress-shielding
Have elastic modulus equivalent to that of the tissue
Co-based alloy manufacture
Casting or powder metallurgy
Ti alloy manufacture
machined
Heat treatment
2
Heating and chilling at a controlled rate
Increased strength or hardness
Heat treatment types
7
Hardening Quenching Annealing Normalizing Tempering Strengthening Surface Hardening
Hardening
Heat and cool rapidly
Quenching
3
Cooling rapidly using salt water, water, oil, molten salt, air or gas
Increased residual stresses and sometimes cracks
Annealing
4
Heat and cool slowly
Reduces hardness
Removes residual stresses
Improve toughness
Normalizing
3
Air cooled
Enhanced hardness
Less ductility
Tempering
4
2nd Heating (lower temp) and cooled slowly
Reduces brittleness
Increased ductility and toughness
Relieves stresses
Strengthening
Controls grain size
Surface Hardening
3
Heat/cool or chemical bath
Improves wear resistance
Lower impact resistance and fatigue life
What are the most employed biomedical alloys?
Ti, CrCo, SS
Desired properties of metals for in vivo use
3
Wear resistance
Mechanical Properties
Corrosion Resistance
What is the function of the oxide layer?
3
Repassivates
Anti-corrosion
Increases biocompatibility
What are the consequences of accelerate corrosion and metal wear in-vivo?
2
Toxicity
Inflammation
