PSI - Issue 42

P. Ferro et al. / Procedia Structural Integrity 42 (2022) 259–269 P. Ferro et al./ Structural Integrity Procedia 00 (2022) 000 – 000

261

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Solomon et al. (2018) carried out a numerical model of IN625 welding process proposing regression equations for the temperature and stress; however, it was not specified how the model was validated. It must point out that the above mentioned papers didn’t focus on RSs. To fill this gap, gas tungsten arc welding (GTAW) simulation of IN625 was caried out with the main objective to predict residual stresses. The model, validated through residual stresses X-Ray diffraction (XRD) measurements, is thought to be a powerful tool in welding process design of such kind of superalloy, even used for repair operations. 2. Materials, geometry, and method 2.1. Experimental investigation The composition of the parent (IN625) and filler metal (ERNiCrMo-3) used in the experiments are summarized in table 1.

Table 1. Chemical composition of the parent and filler metals (wt%). Ni C Mn S Cu

Si

Cr

P

Others

PM: Inconel 625 FM: ErNiCrMo-3

Min 58 Min 64

Max 0.1 Max 0.1

Max 0.5 Max 0.5

Max 0.015 Max 0.015

Max 0.5 Max 0.50

Max 0.5 Max 0.50

20-23

Max 0.015 Max 0.015

Fe 5, Al 0.40, Mo 8-10, Ti 0.1 Fe 1.0, Al 0.40, Nb 3.6 4.5, Mo 0.015, Ti 0.40

22.0 23.0

Plates 100 mm x 60 mm x 5 mm (Fig. 1) were butt welded using a multi-pass arc welding process (GTAW) whose parameters are collected in table 2.

Fig. 1. Cross section of the butt-welded joint with dimensions (mm) and V-groove shape.

Table 2. Welding process parameter. Pass No Current (I) (Amps)

Voltage (V) (Volts)

Root gap (mm)

Argon Gas Flow rate (LPM)

Time for each pass (Sec)

Pass-1 Pass-2 Pass-3

145 145 145

15 15 15

36 31 27

2

12

An inter-pass temperature of about 200 °C was maintained between the passes to avoid hot cracking. Residual stresses were measured by means of XRD technique. Fig. 2 shows a schematic of the goniometer used for detecting the Bragg’s angle used in the Bragg’ s law (Eq. (1)): n λ = 2dsin θ (1) where n refers to the order of reflection beam, d is the interplanar lattice spacing,  is the wavelength of the incident wave and  is the scattering angle. The residual stress was measured on the top surface of the welded joint in the transverse direction. More in detail, their calculation was carried out via Eq. (2): (2) σ φ = m d 0 E 1 + ν æ èç ö ÷ø