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The 17–4 Precipitation Hardening Stainless Steel (PH SS) manufactured by Selective Laser Melting (SLM) has wide application perspectives, but they are limited due to defects and anisotropy. The selection of the appropriate process variables plays a fundamental part in the microstructure and in the determination of the final mechanical and corrosion properties. The main purpose of this study is to analyze the corrosion behavior, hardness and microstructure of 17–4 PH SS manufactured by SLM in comparison to the commercial counterparts. The anisotropic behavior was investigated by analyzing the microstructure–hardness and corrosion interrelationship, both in the surface of the construction platform and in the growth direction of the element. The corrosion behavior of the SLM 17–4PH SS in its natural state was investigated in relation to that of the 17–4 PH SS heat treated in a 0.1 M NaCl + 0.5 M H2SO4 solution, using three electrochemical techniques. The results confirmed that the corrosion resistance of SLM 17–4 PH SS was considerably better than that of the forging, even after 60 days of immersion in the test solution. This was attributed to the absence of important manufacturing defects, to the fine microstructure with an important amount of austenite produced by SLM, and to a small amount of non-metallic inclusions precipitated as a result of the fast cooling and the high speed of solidification associated with the SLM process. [ABSTRACT FROM AUTHOR]

Medical implants manufactured using biomaterial Ti-6Al-4V exhibit some disadvantages. Its higher elastic modulus than that of natural bone can cause stress shielding problems. This can be avoided using Ti-6Al-4V with pores in the implant structure. However, poor corrosion and tribocorrosion behaviors are yielded because of the large area exposed to the medium. To mitigate both issues, coating technologies can be applied. The plasma electrolytic oxidation (PEO) process is a cost-effective process that has been used successfully in nonporous Ti alloys. In this study, two PEO coatings with different amounts of Ca/P are used. However, reports regarding their application in porous materials are scarce. The effects of PEO treatments on corrosion and tribocorrosion in Ti-6Al-4V powder metallurgy are analyzed herein. The porous materials provide an efficient surface for PEO coatings, as demonstrated via scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the porosity of the substrates improved the adherence of the coatings. The corrosion resistance measured via electrochemical impedance spectroscopy confirmed the beneficial effect of the coatings, particularly for long exposure time. The lower roughness, small pore size, and more compact film observed in the PEO-Ca/P sample resulted in favorable tribological and corrosion properties. [ABSTRACT FROM AUTHOR]