Speaker
Description
Selective Laser Melting (SLM) has attracted major interest among the Additive Manufacturing methods (AM). SLM can deliver high manufacturing quality by adjusting production parameters on a given alloy which impacts on the grain structure, phase formation, microstructure, roughness, and porosity. AM aims to achieve superior or even comparable properties to the conventionally manufactured parts. Among the metallurgical features, surface integrity characteristics such as distorted subsurface microstructure and roughness primarily determine the functional life, especially in corrosive environments.
The present study involves the 18Ni-C300 Μaraging steel, an alloy with high strength and toughness and compares its behavior in fatigue resistance depending on the manufacturing method. Τhe comparison is made between conventionally manufactured specimens from a rolled bar and different post-treated SLM-fabricated specimens of the same geometry. The post-treatments refer to surface polishing, shot peening and heating. Experiments were performed in corrosion free and in 3.5% wt. NaCl aqueous solution. Metallography, microscopy (optical and electron), surface scanning, finite element analysis and hardness measurements were employed to help explain the results obtained. The rolled material show a both under pure fatigue and corrosion-fatigue, because of its dense and homogeneous microstructure, as well as its lower resulting surface roughness compared to the SLM. The “as received” SLM specimens, due to the distorted microstructure, but primarily to the higher roughness, showed an inferior fatigue and corrosion-fatigue performance which, however, improves with combination of shot peening and polishing in neutral environment. On the contrary, residual stresses imposed by shot peening have a negative impact on a corrosive environment. Heat treatment does not seem to have a positive effect in high stress fatigue life, however, increases the fatigue endurance limit.
| Speaker Country | Greece |
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