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9 figures, 2 tables.-- Supplementary information available., Concern for the perpetuation of stone monuments is deeply ingrained in humans; however, despite the attempts made in this field, there is still a great deal of effort needed to bring about advancements in the conservation of ornamental stone. Erosive agents, such as rain, extreme temperatures, and chemical and biological agents, threaten our stone heritage and gradually wear away buildings, sculptures, and other monuments found all around the world. Limestone and dolostone have been widely used throughout history, given their ease of extraction and workability. Nevertheless, these properties make them particularly vulnerable to the aforementioned erosive agents, for which the main solution at present is costly and time-consuming restoration. Given the scarcity of effective and durable agents to prevent the deterioration of ornamental and heritage stones, and as graphene oxide (GO) has recently shown impressive effectiveness for this task, this work will further explore the viability of GO as a protective coating for monumental dolostone. For this purpose, GO is sprayed over dolostone surfaces by water dispersion with no adjuvants. The coating performance is assessed in terms of thermal stress, optical inspection (structured light 3D scanner), colorimetry, leachate analysis, and electron microscopy. The main results show that spray-coated GO over stone surfaces creates a highly protective and durable barrier without altering their aesthetic qualities., This research received funding from the University of León (ULE-PoC 2018) and Fundación General de la ULE y de la Empresa (FGULEM) under projects 2019/00149/001 and 2020. This research was also funded through an awarded MICINN project (PID2020-120439RA-I00). The authors are also thankful to the “Applied innovation against climate change and other aggressions on stone monuments (PRESERVARTE)” project of the Regional Ministry of Culture and Tourism of Castilla y León, which will be used to complement this research in the future.

In this paper, the microstructure, defects, hardness, and tensile strength of the 17-4PH specimens manufactured additively using the selective laser melting (SLM) technique were studied. The analyzed parts (10 mm size cubic specimens and tensile specimens) were manufactured with different defocus parameter values (−1, 0, +1 mm) in order to evaluate this effect with a low power laser (38 W). The study was carried out on three different sections of each cubic specimen, one perpendicular to the laser beam or SLM manufacturing direction (transversal section), and another two parallel to the laser beam direction (longitudinal sections). The specimens microstructures were analyzed with an X-ray diffraction technique, as well as optical, scanning electron, and transmission electron microscopes. Image J software was used to characterize the defects and phase ratio. In addition, hardness and tensile tests were performed according to the corresponding standards. The results show that the amount of austenitic phase and the average grain size varied with defocusing. The percentage of defective area was less than 0.25%. The analyzed defocus distance did not affect the number and average size of the defects. Adjusting the defocusing SLM parameter is important for manufacturing parts with good mechanical properties.

Nowadays, metal additive manufacturing techniques, such as Selective Laser Melting (SLM), are becoming more important due to their ability to manufacture very complex functional components. This ability is very interesting to industries as aerospace and automotive. Nevertheless, the installation of this techniques isn’t as could be expected, mainly because of the high-quality requirements of the parts used in these industries. In this work the influence of several specific scanning strategy parameters and the post Heat Treatment (HT) used upon the microstructure and the hardness of the SLM parts have been analysed. For that, several stainless steel 17-4PH specimens were manufactured. Then, two different HTs were applied: stress relieving HT and stress relieving in combination with solution annealing and aging HTs. The hardness, microhardness and metallography general quality, were analysed for each specimen in order to determine the influence of the entire process in the quality of the parts.