Abstract
Selective laser melting has received a great deal of attention in recent years. Nevertheless, research has been mainly focused on the technical issues and their relationship with the final microstructure and monotonic properties. Fatigue behaviour has rarely been addressed, and the emphasis has been placed on high-cycle regimes. The aim of this paper is, therefore, to study, in a systematic manner, the cyclic plastic behaviour of AISI 18Ni300 maraging steel manufactured by selective laser melting. For this purpose, low-cycle fatigue tests, under fully-reversed strain-controlled conditions, with strain amplitudes ranging from 0.3% to 1.0%, were performed. After testing, fracture surfaces were examined by scanning electron microscopy to identify the main fatigue damage mechanisms. The analysis of results showed a non-Masing material, with a slight strain-softening behaviour, and non-linear response in both the elastic and plastic regimes. In addition, this steel exhibited a very low transition life of about 35 reversals, far below the values of conventional materials with equivalent monotonic mechanical properties, which can be attributed to the combination of high strength and low ductility. The total strain energy density, irrespective of strain amplitude, revealed itself to be a quite stable parameter throughout the lifetime. Finally, the SEM analysis showed for almost all the tested samples cracks initiated from the surface and inner defects which propagated through the rest of the cross section. A ductile/brittle fracture, with a predominance of brittle fracture, was observed in the samples, owing to the presence of defects which make it easier to spread the microcracks.
Highlights
Competitiveness at a global scale forces industry to develop efficient manufacturing processes and to reduce the product development cycles
This paper aims at studying the cyclic deformation behaviour of AISI 18Ni300 maraging steel manufactured by selective laser melting, as well as evaluating its cyclic mechanical properties
Low-cycle fatigue tests are performed under fully-reversed strain-controlled conditions, with strain amplitudes lying between 0.3–1.0% in air at room temperature, using a constant strain rate
Summary
Competitiveness at a global scale forces industry to develop efficient manufacturing processes and to reduce the product development cycles. SLM products have a cast structure, high superficial roughness, microstructural heterogeneities, presence of pores, and thermal stresses, which are consequences of pronounced temperature gradients and significant cooling rates Despite these drawbacks, several studies have suggested that their monotonic properties can be similar to those of the components manufactured using conventional processes [3]. This paper aims at studying the cyclic deformation behaviour of AISI 18Ni300 maraging steel manufactured by selective laser melting, as well as evaluating its cyclic mechanical properties. For this purpose, low-cycle fatigue tests are performed under fully-reversed strain-controlled conditions, with strain amplitudes lying between 0.3–1.0% in air at room temperature, using a constant strain rate.
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