PSI - Issue 82

S.S.M. Tavares et al. / Procedia Structural Integrity 82 (2026) 192–198 Tavares et al. / Structural Integrity Procedia 00 (2026) 000–000

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Table 2.Heat treatments performed. Heat treatment

Identification

As Received (cold worked)

AR

AR + 850°C/15 minutes and water cooling (WC) AR + 850°C/30 minutes and water cooling (WC) AR + Solution treatment at 1100°C/WC (ST) ST + 850°C/15 minutes and water cooling (WC) ST + 850°C/30 minutes and water cooling (WC) AR + 1100 o C/30 minutes and slow cooling (furnace)

AR-850-15 AR-850-30

ST

ST-850-15 ST-850-30

1100-SC

Specimens were subjected to non-destructive analysis with ferritoscope (magnetic method) and linear sweep voltammetry (LSV-electrochemical method). After non-destructive tests (NDT), the specimens were cut and machined for Charpy impact tests, Vickers hardness test, and detailed microstructural analysis. The analysis with ferritoscope is based on the magnetic permeability of the sample (Tavares et al., 2010). Since the deleterious phases precipitation in general result from the decomposition of the ferromagnetic ferrite phase ( d ® c , d ® s , d ® s + g 2 ), magnetic methods can be used to detect the embrittlement associated with these reactions. A Helmut Fischer Ferritoscope FMP30 was used to analyze specimens before and after the heat treatments. Ten measurements per specimen were carried out. Linear sweep voltammetry (LSV) was carried out in a portable microcell with Ag/AgCl reference electrode, a Pt wire as counter electrode and the SDSSs specimen as working electrode. The apparatus is schematically shown in Fig.1. The test solution was 3.55 mol.L -1 KOH. The test is controlled by a potentiostat. After the stabilization of the open circuit potential, the potential is increased in the anodic sense with a scan rate 3.42 mV.s -1 . The current density is recorded as a function of the potential. Charpy specimens were V-notched subsize (10 x 3.3 x 55 mm). The impact tests were performed at -46 o C in a Universal pendule with a maximum capacity of 300J. For Vickers hardness determination each specimen was tested with 8 indentations with a load of 10 kgf. Microstructures were investigated in the optical (OM) and scanning electron microscopes (SEM). For the determination of ferrite and austenite contents, the specimens were etched with Behara’s reagent (80ml H 2 O + 20ml HCl + 0.3g potassium metabisulfite) and observed in the OM. The quantification of deleterious phases was assessed in the SEM with samples prepared by grinding and polishing with diamond pastes 6, 3 and 1 µ m. The contrast between the phases d , g , s and c was obtained in the backscattering electrons (BSE) images. Phase quantifications were assessed by digital image processing (DIP) using image J software (Schneider et al., 2012).

Fig. 1. Apparatus for LSV test.