Abstract
Nitrogen is used as an alloying element, substituting the expensive and allergenic element nickel, in austenitic stainless steels to improve their mechanical properties and corrosion resistance. The development of austenitic stainless steel powders with increased nitrogen content for laser additive manufacturing has recently received great interest. To increase nitrogen content in the austenitic steel powders (for example AISI 316L), two measures are taken in this study: (1) melting the steel under a nitrogen atmosphere, and (2) adding manganese to increase the solubility of nitrogen in the steel. The steel melt is then atomized by means of gas atomization (with either nitrogen or argon). The resulting powders are examined and characterized with regard to nitrogen content, particle size distribution, particle shape, microstructure, and flowability. It shows that about 0.2–0.3 mass % nitrogen can be added to the austenitic stainless steel 316L by adding manganese and melting the steel under nitrogen atmosphere. The particles are spherical in shape and very few satellite particles are observed. The steel powders show good flowability and packing density, therefore they can be successfully processed by means of laser powder bed fusion (L-PBF).
Highlights
Austenitic steels are non-magnetic stainless steels that contain high levels of chromium and nickel and low levels of carbon
The steel powders show good flowability and packing density, they can be successfully processed by means of laser powder bed fusion (L-PBF)
Due to the combination of high strength, high toughness and improved corrosion resistance, high nitrogen steels (HNS) with up to 0.9 mass % N in solid solutions have become an important class of engineering materials [7,8,9]
Summary
Austenitic steels are non-magnetic stainless steels that contain high levels of chromium and nickel and low levels of carbon. Among them are austenitic stainless steels with low nickel and high nitrogen content, classified as AISI 200-series. Laser additive manufacturing is an emerging technology [10,11,12,13] with unique capabilities to produce geometrically complex components that is suited for small batch production, weight reduction, part-customization, and functional integration [14,15,16] These advantages known to be relevant to high-cost alloys (superalloys or titanium alloys) and aerospace applications, are significant for austenitic stainless steels. In order to further improve corrosion resistance and mechanical properties, nitrogen can be added into the austenitic stainless steels to be processed by laser additive manufacturing. The flowability and packing density of the powders was determined
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