82
Chapter 2
8. Environment, kh
The effects of tap and salt water on steel are shown in Figure 2.14. The same
effects for nonferrous metal [2.11,2.47] for all tensile strengths over 6 }kh are
0.40 < kh _< 0.64 kh(0.52, 0.040)
(2.76)
Two exceptions are electrolytic copper and copper-nickel alloys for which
0.85 _< k~ _< 1.06, kt,(0.955, 0.035)
(2.77)
and nickel-copper alloys for which
0.64 < k~ < 0.86, k~(0.75, 0.0367)
(2.78)
These results are from tests conducted from 1930-1950; therefore, care
should be taken with newer alloys.
The effect of steam on steel under pressure is
0.70 < kj, < 0.94, k~(0.82, 0.040)
(2.79)
However, for a jet of steam acting in air on steel the values are one-half of
Eq. (2.79).
A corrosive environment on anodized aluminum and magnesium
yields
0.76 _< kh _< 1, kh(0.88, 0.040)
(2.80)
while for nitrided steel
0.68 < k~ _< 0.80
kh(0.74, 0.020)
(2.81)
9. Surface Treatment and Hardening, &
Surface treatment protects the surface from gross corrosion. Results [2.12]
for chrome plating of steel are represented by the reduction of the fatigue
strength
Y = 0.3667 - 9.193 x 10-3a~
(2.82)
where ae 1 is the fatigue strength of the base material. Then ki is
k~ = 1 + Y
(2.83)
For nickel plating [2.54], Yis -0.99 in 1008 steel and -0.33 in 1063 steel. If
shot peening [2.9] is performed after nickel and chrome plating, the fatigue
strength can be increased above that of the base metal.