Crack Paths 2006

- Fractured specimen transversal cutting, corresponding to different crack length

(applied ' Kvalues = 10, 15, 20 MPa¥m);

- Metallographic preparation of the section (up to 0.2 P m Al2O3 powder)

- Chemical attack performed in a 10 ml H N O 3+ 20 ml HCl + 30 ml H2Osolution

for about 15 minutes.

Figure 2. Fatigue crack propagation in hydrogen charging conditions experimental

apparatus.

R E S U L TASN DDISCUSSION

Stress ratio and loading conditions influence on superduplex fatigue crack propagation

resistance is shown in Fig. 3.

10-6

10-87

In air

R = 0.1

R = 0.5

101-100 -9

10

R = 0.75

Underhydrogencharging

R = 0.1

R = 0.5

R = 0.75

3

50

' K [MPam1/2]

Figure 3. Stress ratio and environment influence on 25 Cr 7 Ni stainless steel fatigue

crack propagation resistance.