PSI - Issue 54

Nikolai Kashaev et al. / Procedia Structural Integrity 54 (2024) 361–368 Kashaev et al. / Structural Integrity Procedia 00 (2023) 000 – 000

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on small specimens taken at different heights of the WAAM-fabricated structure. Used welding parameters are included in Table 1. Optimized parameters and the procedure to obtain them are explained in detail in previous work (Vazquez et al., 2021).

Table 1. CMT welding parameters for the manufacturing of the WAAM structure. Mode Current (A) Wire feed speed (m/min) Voltage (V) Travel speed (cm/min)

Dwell time (min)

140

8.5

15.8

60

9

Continuous

As filler metal, a wire of Ti-6Al-4V Grade 5 with a diameter of 1.2 mm certified by AWS: A5.16 & AMS 4945H was used. The chemical composition of the wire, given by the provider, is shown in Table 2. A substrate of the same alloy with equivalent chemical composition and 25 mm thickness was used. The substrate was clamped to a steel plate during the deposition.

Table 2. Chemical composition (wt.-%) of the used Ti-6Al-4V filler wire according to the material manufacturer. Al V Ti Fe C O N H Y other 6.26 4.17 balance 0.15 0.024 0.14 0.006 0.003 0.002 < 0.2

The strategy followed for the manufacturing of the wall consisted of the deposition of a sequence of a pair of layers in which the welding direction was alternated from layer to layer, and following an oscillating strategy as it is detailed in Fig. 1. In the x - y plane, 30 mm of oscillating width, a 4 mm step size and a corner radius of 0º was used. The torch was oriented perpendicularly to the substrate. An offset in z -direction of 3.5 mm between layers was used. The contact tip-work piece distance (CTWD) was kept constant at 13 mm. A dwell time of 9 minutes between depositions of consecutive layers was used to allow interpass cooling (interpass temperature of approx. 60 °C). Following the above mentioned strategy, a wall of 140 mm × 189 mm × 30 mm dimensions was built as it is shown in Fig. 2(a-b). The WAAM-fabricated structure was thermally treated at 920 ºC for 5 hours in high vacuum (< 10 -4 mbar) to provide the required microstructure and tensile mechanical properties as concluded in the previous work (Vazquez et al., 2021).

Fig. 1. Build strategy followed for the manufacturing of the WAAM wall.

Fig. 2. (a-b) Photo of WAAM-fabricated Ti-6Al-4V structure; (c) sketch for extraction of the fatigue (stress-number of cycles, SN) and compact tension C(T)50 specimens.