PSI - Issue 23

First page Table of contents Previous page 242 Next page Last page

Hugo Wärner et al. / Procedia Structural Integrity 23 (2019) 354–359 Hugo Wärner / Structural Integrity Procedia 00 (2019) 000 – 000 Hugo Wärner / Structural Integrity Procedia 00 (2019) 000 – 000 Hugo Wärner / Structural Int it (2019) 0 – 0

3 3

356

Table 1. Chemical composition (in wt.%) of the austenitic alloys. Table 1. Chemical composition (in wt.%) of the austenitic alloys. Table 1. Chemical omposition (in wt.%) of the austenit c alloys.

Material Material Sanicro 25 Sanicro 25

C C

Cr Cr

Ni Ni

W W 3.6 3.6

Co Co 1.5 1.5

Cu Cu 3.0 3.0

Mn Mn n 0.5 0.5 0.6 0.5 0.6 0.6 6.3 6.3 6.3

Nb Nb 0.5 0.5 0.5

Si Si

V V

Mo Mo

Ti Ti

Al Al

Fe Fe

Material

0.1 0.1

22.5 22.5 20.5 20.5

25.0 25.0 30.5 30.5

0.23 0.23

0.2 0.2 0.6 0.6 0.5 0.5

- - - -

- -

Bal Bal Bal Bal Bal Bal

Sanicro 25

0.1

22.5

25.0

3.6

1.5

3.0

0.23

0.2

Bal

Sanicro 31HT Sanicro 31HT Esshete 1250 Esshete 1250

0.07 0.07

- - - -

- - - - - -

- - - -

0.5 0.5

Sanicro 31HT

0.07

20.5

30.5

0.6

0.5

Bal

0.1 0.1

15 15

9.5 9.5

0.3 0.3

1.0 1.0

- -

Esshete 1250

0.1

9.5

0.5

0.3

1.0

Bal

3. Results and discussion 3. Results and discussion 3. Results and discussion 3.1. Mechanical test results 3.1. Mechanical test results 3.1. Mechanical test results

In Fig. 1, the mechanical TMF-test results can be seen for the pre-aged austenitic stainless steels. Fig. 1 a), shows the hardening/softening behaviour and it can be seen that stress levels are similar for the two TMF-test condition for each material. However, there are a difference at the end of the TMF-testing where the IP-cycled tests show softening in contrast to the OP-cycled tests which show continuous hardening, but most of them are fixed to 500 cycles and probably haven´t reached half -life yet. When comparing the response of the materials it is clear that Sanicro 25 suffer higher stresses during the strain controlled TMF-testing and this is due to its prominent hardening behaviour. This has also been seen by Wärner et al. (2018 a) and by the work of Heczko et al. (2018), this is explained by the precipitation of Cu-rich nanoparticles and mainly by the strain induced NbC, NbN and Nb(C,N) precipitates that obstruct the dislocation movement and acts as incoherent dispersoids. Although this promotes hardening, it can be seen in Fig. 1, b) that there is an opposite relation for the plastic strain, where Sanicro 25 show lower levels than the other materials. It should be noted that Esshete 1250 where tested at a lower mechanical range (Δε mech = 0.3%). In general, the IP cycled tests show higher plastic strain for all the investigated materials. However, almost all the continuous OP-cycled tests experienced a gradual barrelling effect of the specimens gauge length and this is showed in Fig. 2. When this effect was accumulated to a certain degree, the thermocouple lost traction and the temperature cycle changed (to RT) which rendered the specimens as failed and no further microstructural investigation, in order to explain the mechanical behaviour, was possible. Only one specimen (Sanicro 31HT, Δε mech = 0.4%) failed according to the prescribed method and therefore tests were conducted with a fixed amount of cycles (N = 500) to ensure comparable test data. In Fig. 1, the mechanical TMF-test results can be seen for the pre-aged austenitic stainless steels. Fig. 1 a), shows the hardening/softening behaviour and it can be seen that stress levels are similar for the two TMF-test condition for each material. However, there are a difference at the end of the TMF-testing where the IP-cycled tests show softening in contrast to the OP-cycled tests which show continuous hardening, but most of them are fixed to 500 cycles and probably haven´t reached half -life yet. When comparing the resp se of the aterials it is clear that Sanicro 25 suffer igher str sses during the strain controlled TMF-testing an t i i t its prominent hardening behaviour. This has also been seen by Wärner et al. (2018 a) and by the work of H l. ( 18), this is explained by the precipitation of Cu-rich anoparticles and mainly by the strain indu d Nb Nb(C,N) precipitates that obstruct the dislocation movement and acts as incoherent dispersoi s. h s r motes hardening, it can be seen in Fig. 1, b) hat there is an opposite relation for the plastic strain, h re 5 s w lower levels than the other materials. It should be noted that Essh te 1250 where tested at a l w i l range (Δε mech = 0.3%). In general, the IP cycled tests show higher plastic strain for all the investigate at ri ls. wever, almost all the continuous OP-cy led tests experienced a gradual barrelling effect of the speci ens gauge length and this is showed in Fig. 2. When this effect was accumulated to a certain degree, the thermocouple lost traction and the temperature cycle changed (to RT) which rendered the specimens as failed and no further microstructural investigation, in order to explain the mechanical behaviour, was possible. Only one specimen (Sanicro 31HT, Δε mech = 0.4%) failed according to the prescribed method and therefore tests were conducted with a fixed amount of cycles (N = 500) to ensure comparable test data. In Fig. 1, the mechanical TMF-test results can be seen for the pre-aged austenitic stainless steels. Fig. 1 a), shows the hardening/softening behaviour and it can be seen that stress levels are similar for the two TMF-test condition for each material. However, there are a difference at the e d of t e TMF-testing where the IP-cycle tests show softeni g in contr st to th OP-cycled tests which show continuous hardening, but most of them are fixed to 500 cycles and probably haven´t reached half -life ye . When compari the response of the materials it is clear that Sanicro 25 suffer higher stresses during the strain controlled TMF-testing and this is due to its prominent harde ing e aviour. Th s has also been seen by Wärner et al. (2018 a) and by the work of Heczko et al. (2018), this is explained by the precipitation of Cu-rich nanoparticles and mainly by the strain induced NbC, NbN and Nb(C,N) precipitates that obstruct the dislocation movement and acts as incoherent dispersoids. Although this promotes hardening, it can be seen in Fig. 1, b) that ther is an opposite relation for the plastic strain, where Sanicro 25 show lower levels than the other materials. It should be noted that Esshete 1250 where tested at a lower m chanical range (Δε mech = 0.3%). In general, the IP cycled tests show hi her plastic strain for all the investigated materials. However, almost all th co tinuous OP-cycled tests experienced a gradual barrelling effect of the specimens gauge length and this is showed in Fig. 2. When this effe t was accumulated to a certain degree, the thermocouple lost traction and the temperature cycle changed (to RT) which rendered the specimens as failed and no further microstructural investigation, in order to explain the mechanical behaviour, was possible. Only one specimen (Sanicro 31HT, Δε mech = 0.4%) failed according to the prescribed method and therefore tests were conducted with a fixed amount of cycles (N = 500) to ensure comparable test data.

Fig. 1. Mechanical results from TMF-testing, a) Stress amplitude vs cycles, b) Plastic strain range vs cycles.

Fig. 1. Mechanical results from TMF-testing, a) Stress amplitude vs cycles, b) Plastic strain range vs cycles. Fig. 1. Mechanical results from TMF-testing, a) Stress amplitude vs cycles, b) Plastic strain range vs cycles.

Made with FlippingBook - Online Brochure Maker