Effect of multiple technologies on minimizing the residual stresses in additive manufacturing
Résumé
Additive Manufacturing (AM) is rapidly becoming the directing technology for manufacturing components in many industries, including automotive, aerospace, medical, etc. Wire-arc additive manufacturing (WAAM) technology with a higher rate of deposition is becoming prominent technology in AM. Wire-based additive manufacturing involves high heat input for melting the wire for deposition. While the component builds up in multiple layers, it involves various heating and cooling cycles, causing non-homogenous thermal loads. Due to repeated cycles, residual stresses get trapped inside the parts and lead to various defects such as cracks, deformation, warpage, the reduced life cycle of the components, etc. It is required to reduce the residual stresses to minimize the defects. This paper talks about the effect of multiple technologies such as pre-heating and compressive loading by hammering to minimize the residual stresses. Pre-heating the substrate (over which deposition takes place) will decrease the thermal gradient and thus, reduce the residual stress. Since tensile residual stresses are generated during the wire-based cladding process, which is to be nullified by applying compressive loading, a pneumatic-based setup developed in-house for imparting the compressive residual stresses was used to minimize the tensile residual stresses. In this work, four different samples were prepared; 1) as-deposited (without pre-heating and hammering), 2) deposition followed by hammering, 3) preheating then deposition, 4) Pre-heating followed by deposition and then hammering to measure the residual stress through the X-ray diffraction method. It was found that pre-heating and hammering individually minimize the residual stresses, and the combined effect has shown much reduction in tensile residual stress.
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