Effect of interlayer surface preparation on microstructures and mechanical properties of wire and arc additive manufactured low carbon steel objects

The workpiece fabricated by wire and arc additive manufacturing is usually made up of hundreds of welds. If the slag is not cleaned up and adherent to the weld surface, it will be stuck in welds and becomes inclusions and other defects within the structures. This is not only the case when using flux cored wire as the consumable material, but also with solid wire. Different weld morphologies were studied by controlling the slag treatment after each layer deposition, in terms of non-destructive test (X-ray radiographic testing). Further investigation of the microstructures and composition of slag inclusions were developed by SEM and EDS analysis. Charpy V-notch impact test has been conducted on the specimens both in vertical and horizontal direction to the deposition direction and tested at 0°C, −20°C and −60°C. The fracture surfaces of the specimen made without any slag treatment after deposition exhibit large number of welding defects, which is highly responsible for lowering the impact toughness. On the other hand, completely clear away of the slag by extensively inter-pass grinding gives rise to a fine grain structure and relative high impact toughness, however, a huge sacrifice of the production efficiency and high material waste is unavoidable.