Purpose Wire + arc additive manufacturing (WAAM) uses existing welding technology to make a part from metal deposited in an almost net shape. WAAM is flexible in that it can use multiple materials successively or simultaneously during the manufacturing of a single component. Design/methodology/approach In this work, a gas metal arc welding (GMAW) based wire + arc additive manufacturing (WAAM) system has been developed to use two material successively and fabricate bimetallic additively manufactured structure (BAMS) of low carbon steel and AISI 316L stainless steel (SS). Findings The interface shows two distinctive zones of LCS and SS deposits without any weld defects. The hardness profile shows a sudden increase of hardness at the interface, which is attributed to the migration of chromium from the SS. The tensile test results show that the bimetallic specimens failed at the LCS side, as LCS has lower strength of the materials used. Originality/value The microstructural features and mechanical properties are studied in-depth with special emphasis on the bimetallic interface.

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2016)Porosity formation mechanisms in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steels, Science and Technology of Welding and Joining, 21:3, 209-215,The porosity formation in cold metal transfer (CMT) gas metal arc welding (GMAW) of zinc coated steel is studied over a wide range of the heat inputs (160-250 J mm 21 ), which shows low porosity in weld bead (,2% of bead area) in low (,250 J mm 21 ) and high (.350 J mm 21 ) heat inputs and maximum at medium (250-350 J mm 21 ) heat inputs. The high speed imaging of weld pool shows that the highest frequency of zinc vapour escapes at high heat inputs compared to other conditions. Numerous experiments show that size and location of pores along with escaping of zinc vapour are the results of competition of viscosity of weld pool against buoyancy and vapour pressure within the time required to reach solidification temperature. Based on this concept, mechanisms involved in porosity formation, growth and escape phenomena are disclosed, which can help select the optimised welding conditions to obtain porosity free welds in CMT-GMAW of zinc coated steels.

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