Biomedical Engineering Reference
In-Depth Information
steel are favored in acetabular and pelvic surgery and at other
anatomical locations.
Due to their high nickel content (10-14%), stainless steel
implants can cause negative tissue reactions and dermatitis
(Table 3.10) [24, 76]. Moreover, the nickel ions released during
corrosion of the device are reported to cause allergies and even
cancer [76]. The World Health Organization (WHO) estimated that
a content of less than 0.2% of nickel is congruous with medical
requirements [24]. Therefore the development of materials with
improved corrosion resistance and without nickel is absolutely
imperative. One of the most promising austenitizing elements to
replace nickel is nitrogen [103]. Nitrogen increases the stability
of austenite, enhances corrosion resistance, and prevents the
formation of sigma phase [124]. By this method, small devices with
the ferritic structure can be precisely machined and subjected to
nitrogenization of their surfaces in nitrogen gas at temperature of
about 1200
o
C. They are then nickel-free austenitic stainless steels
with improved mechanical properties and corrosion resistance
[128]. It is expected, that these new stainless steel alloys may have a
similar biocompatibility as cp titanium implants.
Ta b l e 3
.
10
Chemical composition of some 300 grade austenitic stainless
steels
SAE
designation % Cr
% Ni
% C
% Mn % Si
% P
% S
% N
Other
304
18-20 8-10.50 0.08 2
0.75 0.045 0.03 0.1
—
304L
18-20 8-12 0.03 2
0.75 0.045 0.03 0.1
—
304N
18-20 8-10.50 0.08 2
0.75 0.045 0.03 0.10-0.16—
316
16-18 10-14 0.08 2
0.75 0.045 0.03 0.10
2.0-3.0
Mo
316L
16-18 10-14 0.03 2
0.75 0.045 0.03 0.10
2.0-3.0
Mo
316N
16-18 10-14 0.08 2
0.75 0.045 0.03 0.10-0.162.0-3.0
Mo
316LVM 17.57 14.68 0,023 1.84 0.37 0.014 0.01 0.03
2.79 Mo
0.03 Cu
3
.
2
.
2
Cobalt Alloys
Co-Cr-Mo alloys are well used for biomedical applications such as
dental and orthopedic implants owing to their excellent mechanical
