PSI - Issue 42

5

Rui F. Fernandes et al. / Procedia Structural Integrity 42 (2022) 1054–1060 Author name / Structural Int grity Procedia 00 (2019) 000 – 000

1058

Fig. 3. da/dN- ∆K curve s for AB, HIP and 250ºC specimens, R=0.05.

In this sense, HIP treatment didn’t show any advantage when compared with the 250ºC once they have similar heat treatment temperature. Besides that, it was calculated the Paris law parameters that are shown in Table 2.

Table 2. Paris law parameters

Specimens

C (mm/cycle)

m

Cor. Coefficient

As-Built (AB)

3.305×10 -7 2.052×10 -7 2.141×10 -7

3.749 3.267

0.943 0.945 0.991

Hot Isostatic Pressing (HIP)

Stress Relief (250ºC)

3.1

Regarding the linear relation between da/dN and ∆K zone (Paris regime), there was no significant crack closure level for the three series. The U parameter calculated for the three series are shown Figure 4. The average values of the U parameter were 0.999, 0.992, and 1.00 for the As-built, HIP and Stress Relief, respectively. Following the FCG results, the difference of the AB state and heat-treated specimens cannot be justified by the increase in the ductility of the material, since the U parameters have similar values, close to one, which indicates no crack closure level.