Abstract
The paper focuses on researching the effect of fatigue loading on metallic structure, lifetime, and fracture surface topographies in AISI H13 steel specimens obtained by selective laser melting (SLM). The topography of the fracture surfaces was measured over their entire area, according to the entire total area method, with an optical three-dimensional surface measurement system. The fatigue results of the SLM 3D printed steel specimens were compared with those reported for conventionally manufactured 13H steel. The investigation also considers the roughness of the specimens’ side surface. Moreover, the fractographic evaluation conducted using scanning electron microscopy confirms that the predominant fracture mechanism is transgranular fracture. Microtomography done after mechanical loading also showed the influence of the stress level on the porosity distribution. Both fractographic and Micro-CT investigations confirm that higher stresses result in coarser and much more uniform porosity observed in fractured samples. These comprehensive quantitative and qualitative fracture analyses are beneficial to predict the failure conditions of SLM steel parts, especially in the case of fatigue damage. From the quantitative analysis of the H13 SLM-manufactured fracture surface topography, it was possible to conclude that the larger the loadings acting on the specimen, the rougher the fracture surface because the ductile fracture mode dominates. It has also been proven that the porosity degree changes along the length of the sample for the most stressed specimens.
Highlights
Since the 1990s (Beaman and Deckard 1989), additive manufacturing (AM) technologies have been intensely expanded, proper to their versatility as efficient techniques for metal processing (Beaman and Deckard 1989; Carneiro et al 2019; Jesus et al 2021)
In the case of the selective laser melting (SLM) samples, the scatter is higher, which can be explained by the specificities of the manufacturing process which is more susceptible to defects
The fracture surface behaviour of an AISI H13 steel obtained by SLM subjected to uniaxial fatigue loading was characterised using different texture topology parameters
Summary
Since the 1990s (Beaman and Deckard 1989), additive manufacturing (AM) technologies have been intensely expanded, proper to their versatility as efficient techniques for metal processing (Beaman and Deckard 1989; Carneiro et al 2019; Jesus et al 2021). The AISI H13 grade is conventionally dedicated for metal tools subjected to high operation at elevated temperatures. This type of steel has excellent resistance to thermal fatigue, erosion, and sliding wear (Walczak and Szala 2021), and currently, the H13-grade metallic powder is employed to produce moulds and dies using. Investigations into fracture mechanisms are pivotal, for additively manufactured components, because they are highly susceptible to a number of defects, namely micro-cracks and porosities, which may result in material lack of coherence (Romano et al 2020; Wang et al 2019). Numerous mechanisms of crack nucleation and propagation have been described in additive manufacturing materials. Dimples and cleavage of the tensile fracture surface were analysed by Weng et al (2020). The authors pointed out that the fracture behaviour and failure modes of 3D-printed components is essential to ensure safe mechanical stresses during their service life
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