Biomedical Engineering Reference
In-Depth Information
Figure 6.4
Schematic process of obtaining nickel-free stainless steels
[11]. See also Color Insert.
Table 6.2
Comparison of properties of nickel-free ferritic and austenitic
steels
Nickel-free ferritic steels
Nickel-free austenitic steels
Low biocompatibility
High biocompatibility
Good machinability
Poor machinability
Low corrosion resistance
High corrosion resistance
Low strength
High strength
Ferromagnetic
Paramagnetic
Previous methods of producing nickel-free stainless steels
include: melting in induction furnaces, melting in the plasma furnaces,
pressure electroslag remelting, and powder metallurgy combined
with isostatic hot pressing (HIP) [1, 8, 10, 21]. The production by
powder metallurgy uses the following techniques: gas atomization,
nitriding in luidized bed, and rotary furnaces.
Contemporary trends in the development of new materials are
based on the obtaining of nanostructure, which guarantees the
improvement of properties of the inal product. When the grain
size of austenitic stainless steel is constant, the strength increases
with increasing nitrogen content. The following empirical equation,
with the conventional yield strength 0.2% and nitrogen content N,
concerns Fe-Cr-N, Fe-Cr-Mn-N and Fe-Cr-Ni-N austenitic stainless
steels:
