PSI - Issue 3

Francesco Iacoviello et al. / Procedia Structural Integrity 3 (2017) 308–315 Author name / Structural Integrity Procedia 00 (2017) 000–000

313

6

propagation micromechanisms in 800°C tempered 2101 DSS do not correspond to a very embrittled steel: higher critical temperature range in “lean” DSS should be more deeply investigated. “Standard” 2205 DSS and “super” 2507 DSS are prone to be embrittled due to tempering treatments at 800°C: fatigue crack propagation micromechanisms are strongly influenced, with an evident increase of the importance of ferrite cleavage and secondary cracks propagation in ferrite grains or in ferrite/austenite grain boundaries.

10 -6

10 -7

10 -8

da/dN

[m/cycle]

2205 (R = 0.5)

10 -9

solution annealed 800°C - 1h 800°C - 3h 800°C - 10h

10 -10

3

10

50

 K [MPa m 1/2 ]

Fig. 8: 2205 “standard” DSS fatigue crack propagation resistance: heat treatment influence (R = 0.5).

10 -6

10 -7

10 -8

da/dN

[m/cycle]

2507 (R = 0.5)

10 -9

solution annealed 800°C - 1h 800°C - 3h 800°C - 10h

10 -10

3

10

50

 K [MPa m 1/2 ]

Fig. 9: 2507 “super” DSS fatigue crack propagation resistance: heat treatment influence (R = 0.5).

4. Conclusions Austenitic-ferritic (duplex) stainless steels are successfully used in chemical, nuclear, oil and gas industries, due to their good mechanical properties and excellent generalized and localized corrosion resistance in many environments and operating conditions (for example, chloride induced stress corrosion). In this work, three austenitic-ferritic