PSI - Issue 14

P D Gosavi et al. / Procedia Structural Integrity 14 (2019) 304–313

311

P D Gosavi et al./ Structural Integrity Procedia 00 (2018) 000 – 000

welding joints made by other welding processes. This weld has the highest P cm value of 0.27 amongst all the weld joints produced using a moderate heat input of 1.84kJ/mm, table 7.From phase analysis it can be seen that of the four weld processes studied, weld joint W2 has a very high AF content (~79%). Higher volume fraction contributed to enhancement of both tensile properties and sub-zero temperature impact toughness.

Table 7. Comparative Properties of respective weld joints. Welding Process No. of passes Heat Input (KJ/mm) P cm

%AF

DBTT @ -40° C

W1 W2 W3 W4

44 49 63 46

1.3

0.23 0.27 0.22 0.24

71 77 67 74

39

1.85 2.35

191

14 41

27

1.6

3.5. Fractography

The W2 joint made by GTAW process has more toughness value at -40 ° C as around 190 J as ductile fracture indicated in fractography image at 5 KX done by SEM. The substantial amount of energy was absorbed by microvoids coalescence which results in high energy fracture mode of ductile manner as shown in fig.10(b). The fractographs of W1 and W4 indicates mode of fracture with surface consisting of cracks which gives small area of fracture surfaces compared to W2 which indicates brittle fracture but there are considerable percentage of microvoid coalescence which indicates ductile manner as its impact values are 40 J and 41 J it has both fracture percentage as ductile and brittle manner respectively shown in fig. 10(a), 10(e). The W3 joint made by SAW process has more cracks and shear planes comparable to W1 and it indicates stress line pattern so failure of brittle manner is more as shown in fig.10(c), 10(d) and impact toughness is 14 J for subsurface & 27 J for center as lowest among all investigated joints

(a)

Shear Planes

Dimples

(b)

Microvoidal coalescence (Dimples)