Additive manufacturing (AM) is a rapidly growing field of technology. In order to increase the variety of metal alloys applicable for AM, selective laser melting (SLM) of duplex stainless steel 2205 powder and the resulting microstructure, density, mechanical properties, and corrosion resistance were investigated. An optimal set of processing parameters for producing high density (>99.9%) material was established. Various post-processing heat treatments were applied on the as-built predominantly ferritic material to achieve the desired dual-phase microstructure. Effects of annealing at temperatures of 950 °C, 1000 °C, 1050 °C, and 1100 °C on microstructure, crystallographic texture, and phase balance were examined. As a result of annealing, 40–46 vol.% of austenite phase was formed. Annealing decreased the high yield and tensile strength values of the as-built material, but significantly increased the ductility. Annealing also decreased the residual stresses in the material. Mechanical properties of the SLM-processed and heat-treated materials outperformed those of conventionally produced alloy counterparts. Using a scanning strategy with 66° rotation between layers decreased the strength of the crystallographic texture. Electrochemical cyclic potentiodynamic polarization testing in 0.6 M NaCl solution at room temperature showed that the heat treatment improved the pitting corrosion resistance of the as-built SLM-processed material.

Hydrogen solubility and diffusion in austenitic stainless steels, namely AISI 310, AISI 301LN and AISI 201, are studied with thermal desorption spectroscopy (TDS) after electrochemical potentiostatic hydrogen pre‐charging. Temperature dependencies of hydrogen desorption for all studied steels manifest a complex main peak caused by hydrogen releasing from the steel lattice by diffusion. Depending on the steel and heating rate the peak is situated from 350 to 500 K and its shape reflects a specific of hydrogen diffusion in stainless steels, which are multicomponent alloys. Analysis of the TDS curves is based on the hydrogen diffusion model taking into account trapping of hydrogen atoms in the energetically deep interstitial positions in the steel crystal lattice. Diffusion coefficient of hydrogen and its total content after the same charging procedure are obtained from the TDS curves and compared for the studied steels.

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Photocatalytic activity of TiO 2 -coated austenitic stainless steel ͑AISI 304͒ and copper alloys ͓deoxidized high phosphorus ͑DHP͒ copper and Nordic Gold͔ was studied by means of decomposition of methylene blue model waste water and open-circuit electrochemical potential measurements, and the photoinduced hydrophilicity was studied by means of contact angle measurements of water under ultraviolet irradiation. The TiO 2 coatings were prepared by an atomic layer deposition technique from TiCl 4 and H 2 O. The thicknesses of the prepared coatings were 5, 10, 50, 100, 150, and 200 nm. Morphology and crystal structure of the TiO 2 coatings were studied using scanning electron microscope and X-ray diffraction techniques. Photocatalytic activity of the studied coatings was low with a coating thickness of 5 and 10 nm. When the coating thickness was 50 nm or higher for AISI 304 stainless steel, and 100 nm or higher for DHP and Nordic Gold copper alloys, the photoactivity was good, but no saturation or systematic effect of coating thickness or surface finish was observed. The photoinduced hydrophilicity was good with all studied coating thicknesses ͑50, 100, 150, and 200 nm͒, with some exceptions.

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The aim of this study was to characterize the inclusions and precipitates of the six austenitic stainless steel test materials by the INCA analysis program as well as to examine the capability of inclusions and precipitates to act as hydrogen traps by utilizing the thermal desorption spectroscopy (TDS). Especially, the hydrogen trapping capability of nano‐sized Nb‐precipitates of the steel 204Cu/Nb was of interest. On the INCA results it was noticed that the average sizes of the inclusions as well as the distribution and the amount of the oxide inclusions were about the same in all test materials. In comparison to the other grades, the distribution of inclusions and precipitates was significantly different in the niobium‐alloyed 204Cu/Nb steel containing a large number of small micro‐ and nano‐sized niobium precipitates. In the TDS study, it was observed that the TDS spectra of 201B, 204Cu, and 204Cu/Nb were similar, although the inclusion and precipitation distribution of these steels differs considerably between the materials. Thus, it was assumed that the nano‐sized Nb‐precipitates or other inclusions were not able to trap sufficiently hydrogen to their interface, which would result in a better resistance against delayed cracking.