Effect of travel speed and number of layers on surface waviness of ER70S6 deposits fabricated through non-transferred wire arc additive manufacturing

Abstract

The present experimental study introduced NTA-WAAM system for fabricating thin-layered structures using ER70S-6 wire. The study is directed towards determining the Sw in the manufactured parts, considering varying level of TS (0.17, 0.19, and 0.24 m/min) and BL (2, 3, 7 layers). The Sw is computed through image processing using canny edge detection method. Increasing the BL from 2 to 7 and reducing TS from 0.24 to 0.17 m/min, the resulting Sw is increased from 1.05 to 2.69 mm. So with high BL, TS should be more to suitably control the Sw because of high heat dissipation and low fluidity of molten pool. In addition to the morphological attributes, microstructural evolution, XRD, Rietveld refinement, tensile, and wear testing are incorporated to present the feasibility and stability of part fabricated through NTA-WAAM. Crystallite size, dislocation density, and residual stress are computed through XRD. It is observed that when approaching the top section from bottom zone of deposition, crystallite size is reduced from 23.43 to 21.85 nm, whereas dislocation density (2.83 × 1012 to 6.52 × 1012m−2) and residual stress (−263.72 to −300.12 MPa) are increased. It indicates the adverse effect of crystallite size towards dislocation density and residual stress, which is primarily attributed to varying level of heat transfer during deposition. The deposit exhibits an ideally refined crystal structure than initial filler wire as χ2≈1 (from Rietveld analysis). Compressive residual stress development further improves the fabricated part’s tensile characteristics. Formation of equiaxed dimples, characterises the ductile failure phenomena, whereas the enhancement in their dimensions reflects the improvement in ductility.