- See:
Characteristics of Metals and Implants:
- Discussion:
- has best mechanical properties, as it is strong and has good
fatigue resistance;
- it is easily worked and cheap to manufacture;
- serious draw back is the tendency to corrode;
- forged stainless steel has greater
yield strength than cast stainless steel, but has
lower
fatigue strength than other alloys;
- because of femoral component fracture with early designs, stainless
steel is no longer routinely used;
- from the standpoint of erosion, biocompatibility, and
fatigue life, stainless steel
is inferior to other superalloys;
- Corrosion Properties:
- corrodes more easily than other materials;
- addition of chromium and molybdenum to stainless steel produces corrosive
resistant surface layer;
- surfaces of all metal implants in the U.S. are covered using nitric acid to
form an oxide or hydroxide on their surfaces;
-
fretting corrosion:
- a process in which abrasive wear is accompanied by corrosion;
- protective oxide layer on metal is removed by abrasion process;
- because new passivation layer that forms after abrasion is neither as durable
nor as chemically inert as original layer, metal is more susceptible to
corrosion;
- this form of corrosion often occurs between screw heads &
plates;
- stainless steel & cobalt-chromium alloys are susceptible to fretting corrosion;
