Selective Laser Melting (SLM) is a modern manufacturing method with many applications in medicine, aerospace and automotive industries. SLM processed materials are characterized by good dimensional accuracy and properties comparable or superior to materials obtained by traditional processing methods. In this paper an SLM process was used to obtain 316L stainless steel parts. This paper presents the microstructure, chemical and phase composition, physicochemical and electrochemical properties of 12 groups of tested samples, differentiated by the SLM processing parameters. Based on the investigation, it can be inferred that the selection of the appropriate SLM parameters is very important to determined final material properties. The samples produced with the energy density E = 600 J/mm3 were observed to possess optimum properties – a homogeneous structure, density closest to the desired one, good wettability and pitting corrosion resistance.

In the electropolishing process, the polishing quality of the metal surface varies according to the contamination of the electrolyte. In this study, the electrolyte was evaluated according to the usage time, and the effect of each factor on electropolishing was investigated. As the electrolyte is contaminated, the concentration of metal ions in the electrolyte increases and the ion conductivity decreases. In addition, the pH and specific gravity of the electrolyte increase due to the metal sludge formed as the metal ion concentration increases. When the electrolyte usage time was more than 5 days, many scratches remained on the surface of 316L stainless steel, and relatively high surface roughness was measured. The surface roughness improvement rate compared to the initial specimen was 30% for the unused electrolyte, 26% on the 3rd day, 19% on the 5th day, and 17.5% on the 13th day. Since the low current density due to electrolyte contamination causes a decrease in polishing efficiency, initial scratches on the metal surface still exist on the polished surface. Therefore, it is necessary to manage the electrolyte to maintain the quality of electropolishing.

This paper introduces an approach for vacuum brazing of niobium-316L stainless steel transition joints for application in superconducting radiofrequency cavity helium jackets. The study takes advantage of good wettability of Ag-Cu-Pd brazing alloy to suppress brittle Fe-Nb intermetallic formation, hence improve the joints’ mechanical performance. The wettability of Ag-Cu-Pd filler metal on niobium, the interface microstructure and mechanical properties of the transition joints were investigated. Two kinds of Ag-Cu-Pd filler metals had been studied and wet well on the niobium, and the wettability of Ag-31.5Cu-10Pd filler metal on niobium was better than Ag-28Cu-20Pd filler metal. Microstructure characterization demonstrated the absence of brittle intermetallic layers in all of the joint interfaces. Mechanical properties of samples prepared with Ag-31.5Cu-10Pd filler metal were also better than their peers made with Ag-28Cu-20Pd filler metal both room temperature (300 K) and liquid nitrogen temperature (77 K). The transition joints displayed shear strengths of 356-375 MPa at 300 K and 440-457 MPa at 77 K, respectively. After undergoing ten thermal cycles between the room temperature and the liquid nitrogen temperature, the transition joints’ leak rates were all lower than 1.1×10 ^–11 mbar·L/s. Therefore, Ag-Cu-Pd filler metal is applicable to high vacuum vessels used at cryogenic temperatures.

In this work, the 316L austenitic steel based milled and sintered composites with 0.33 wt% and 1 wt% SiC ultra-fine particles addition have been prepared. The high efficient attrition milling provided an efficient size reduction of the 316L steel grains and homogeneous distribution of the SiC nanoparticles before sintering process. Spark plasma sintering (SPS) was used for compaction of milled powder mixtures. The effect of SiC addition on the milling efficiency and the structure of the composites have been studied. It was found that the amount of ceramic addition did not influence the efficiency of milling process, powder mixtures with flake like grains have been obtained. On the other hand, the intensive milling assured an optimal coverage of 316L stainless steel grains with submicron sized ceramic particles in both cases. The sintered composites showed high densities with the presence of small amount of closed porosities. Structural, mechanical and tribological examinations of 316L/SiC composites have been performed and presented.

In this study, 316L stainless steel powder was used to produce a porous body that could be used in a specific environment. In contrast to the existing method of producing filters using only spherical powders, we attempted to produce filters using plate- and needle-like powders and evaluated their performance. In the powder preparation step, the shape change of the powder was analyzed by changing the size of the stainless-steel balls used for ball milling. Then, the variations in properties of the sintered porous body caused by the ball size were investigated. As the average ball size decreased, the average particle size of the powder decreased. Moreover, the surface area and pore size of the porous body decreased. Additionally, when balls of different sizes were mixed, the porous body showed a mixture of coarse and fine pores.