Abstract
Selective Laser Melting (SLM) is currently one of the more advanced manufacturing and prototyping processes, allowing the 3D-printing of complex parts through the layer-by-layer deposition of powder materials melted by laser. This work concerns the study of the fracture toughness of maraging AISI 18Ni300 steel implants by SLM built over two different conventional steels, AISI H13 and AISI 420, ranging the scan rate between 200 mm/s and 400 mm/s. The SLM process creates an interface zone between the conventional steel and the laser melted implant in the final form of compact tension (CT) samples, where the hardness is higher than the 3D-printed material but lower than the conventional steel. Both fully 3D-printed series and 3D-printed implants series produced at 200 mm/s of scan rate showed higher fracture toughness than the other series built at 400 mm/s of scan rate due to a lower level of internal defects. An inexpressive variation of fracture toughness was observed between the implanted series with the same parameters. The crack growth path for all samples occurred in the limit of interface/3D-printed material zone and occurred between laser melted layers.
Highlights
Selective Laser Melting (SLM) refers to layer material addition techniques that allow the generation of complex 3D-printed parts by selectively joining successive layers of powder material on top of each other, using thermal energy supplied by a focused, computer-controlled laser beam.This technology is a very high-energy process, as each layer of metal powder must be heated above the melting point of the metal [1,2]
The SLM process is largely affected by parameters such as laser power, scan speed rate, protective atmosphere, material used in the process and materials to joint, among others
The results show that the majority of tests lead to invalid fracture toughness tests, because the geometry of samples do not guarantee a plain strain state, leading to an excessive plastic deformation at the crack tip
Summary
Selective Laser Melting (SLM) refers to layer material addition techniques that allow the generation of complex 3D-printed parts by selectively joining successive layers of powder material on top of each other, using thermal energy supplied by a focused, computer-controlled laser beam. Bai et al [6] studied the influence of parameters on SLM process and mechanical properties evolution of maraging steel 300 Like previous authors, they prove the considerable influence of the scan rate, laser power and scan spacing as regards the density of a part. The authors of Reference [12] studied the mechanical behavior of selective laser melting 18Ni300 steel specimens, concluding that a very high scan rate (400 or 600 mm/s) causes a high percentage of porosity and a consequent drastic reduction of the tensile strength, stiffness and elongation at failure, compared with the results obtained for a 200 mm/s scan rate. Cyr et al [16] studied the fracture behavior of additively manufactured 18Ni300/H13 hybrid hard steels These authors observed a presence of an interface between the different steels.
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