Additive manufacturing (AM) allows for optimized part design, reducing weight compared to conventional manufacturing. However, the microstructure, surface state, distribution, and size of internal defects (e.g., porosities) are very closely related to the AM fabrication process and post-treatment operations. All these parameters can have a strong impact on the corrosion and fatigue performance of the final component. Thus, the fatigue-corrosion behavior of the 3D-printed (L-PBF) AlSi10Mg aluminum alloy has been investigated. The influence of load sequence (sequential vs. combined) was explored using Wöhler diagrams. Surface roughness and defects in AM materials were examined, and surface treatment was applied to improve surface quality. The machined specimens showed the highest fatigue properties regardless of load sequence by improving both the roughness and removing the contour layer containing the highest density of defect. The impact of corrosion was more pronounced for as-printed specimens as slightly deeper pits were formed, which lowered the fatigue-corrosion life. As discussed, the corrosion, fatigue and fatigue-corrosion mechanisms were strongly related to the local microstructure and existing defects in the AM sample.

Laser beam-powder bed fusion/metal (PBF-LB/M) offers significant advantages for manufacturing 316L stainless steel components. However, inherent surface roughness can limit their application in sectors requiring high-quality surfaces. This study investigates the influence of two electrochemical post-processing techniques, Hirtisation and DLyte, on surface topography and fatigue behavior of PBF-LB fabricated 316L stainless steel. Vertically built cylindrical fatigue specimens were subjected to both the treatments. Following surface treatment, surface roughness, residual stress, microstructure, and high-cycle fatigue properties were studied. Hirtisation significantly reduced the average surface roughness (S _a ) around 70%, with a further improvement to around 80% after DLyte treatment. The mean roughness depth and deepest valley depth also decreased after post-processing. Notably, uniaxial fatigue testing revealed a 20% increase in fatigue life for specimens subjected to Hirtisation while around 40% for a combination treatment, Hirtisation + DLyte compared to the as-built condition. However, these specimens exhibited higher surface tensile residual stress levels. This suggests a trade-off between the benefits of a smoother surface (reduced fatigue crack initiation sites) and the detrimental effects of higher residual stress (promoting crack propagation). Despite the improvement in surface quality, the treated specimens exhibited higher surface residual stress, which may counteract some fatigue benefits.

When subjecting cast irons to mechanical loading the deformation and damage mechanisms occur on a microstructural level and are dependent on the inherent microstructure. A deeper understanding of the relation between the different microstructural constituents and the macroscopic mechanical behaviour would be beneficial in material development efforts and for the ability to design and cast components with tailored properties. Traditionally, microscopy examinations on sectioned cast iron samples have been used when analysing the microstructure in cast irons. Since all microstructural heterogeneity is in three-dimensions (3D), methods that provide a three-dimensional characterisation are essential for a deeper understanding of, both the microstructural features as well as the deformation and damage of cast irons. Therefore, different cast iron grades have been studied using synchrotron X-ray tomography and 3D x-ray diffraction (3DXRD) at ESRF in Grenoble, France. The samples were stepwise loaded and unloaded in-situ at in the tomography/3DXRD set-up to study the deformation with regard to microstructural constituents and the microstructural evolution in 3D. Based on the 3D tomography image sequences, digital volume correlation (DVC) was used for full strain field analysis and for the analysis of damage and deformation mechanisms. In addition, 3DXRD data were analysed to provide details on the lattice parameters and lattice strain of individual ferrite grains. This work shows the possibilities of such synchrotron experiments for advanced study of the mechanical behaviour of cast iron.