Hydrogen embrittlement in power plant steels - Indian Academy of ...

Hydrogen embrittlement in power plant steels 445
10 −4
stress corrosion cracking in water
low alloy steel
10 −5
10 −6
many data at
288 o C, 150 o C, 100 o C
(as Indicated)
data at 20 o C
10 −7 HYDROGEN
da / dt (ms −1 )
10 −8
10 −9
10 −10
288 o C
160 o C
10 −11
100 o C
10 −12
10 −13
0
20 o C
EMBRITTLEMENT
ANODIC DISSOLUTION
200 600 1000 1400
yield strength (MPa)
Figure 18. Influence of yield strength on
crack growth rate of low alloy steel in water
(Magdowski 1987).
effects approaches a lower limit. More than the bulk composition, impurity concentration at
grain boundary is important. Grain boundary segregation is dependent on alloy composition.
Ni, Cr, Mn and Si promote grain boundary segregation.
6. Hydrogen embrittlement mechanisms
From the foregoing information, one can see that hydrogen embrittlement is dependent on
many variables such as temperature, pressure, level and type of stresses, environment, phys-
KTH (MPa m)
120
80
60
0 . 00 0 . 02 0 . 04 0 . 06 0 . 08 0 . 10
BULK P + S CONCENTRATION, w/o
(a)
KTH (MPa m)
100
80
60
40
20
(b)
0
0 . 0 0 . 5 1 . 0 1 . 5 2 . 0
(Mn + 0 . 5 Si + P + S), w/o
Figure 19. Reduction of K IHE as a function of (a) P + S concentration, (b) composition parameter
(Moody & Robinson 1990).