Additive manufacturing (AM) is among the novel industrial technologies for fast prototyping of complex parts made from different constructional and functional materials. This review is focused on phase composition of additively manufactured chromium-nickel austenitic stainless steels. Being produced by conventional methods, they typically have single-phase austenitic structure, but phase composition of the steels could vary in AM. Comprehensive analysis of recent studies shows that, depending on AM technique, chemical composition, and AM process parameters, additively manufactured austenitic stainless steels could be characterized by both single-phase austenitic and multiphase structures (austenite, ferrite, σ-phase, and segregations of alloying elements). Presence of ferrite and other phases in AM steels strongly influences their properties, in particular, could increase strength characteristics and decrease ductility and corrosion resistance of the steels. Data in review give a state-of-art in mutual connection of AM method, chemical composition of raw material, and resultant phase composition of AM-fabricated Cr-Ni steels of 300-series. The possible directions for future investigations are discussed as well.

The paper reports on theoretical study to elucidate the influence of geometric (width) and mechanical characteristics of phase interfaces on strength, ultimate strain, and fracture energy of metal...

We study the effect of ion-plasma surface nitriding on the phase composition, microstructure, surface microhardness, and tensile properties of the AISI 321-type stainless steel produced by wire-feed electron-beam additive manufacturing (EBAM). Ion-plasma nitriding at 550 °C for 12 h in N₂/H₂ gases provides the formation of a 10-μm thick surface layer with solid solution strengthening by nitrogen atoms (Fe-γ_N и Fe-α_N) and dispersion hardening (γ’-Fe₄N) with a fivefold increase in surface hardness up to ≈12 GPa. Surface ion-plasma nitriding of additively produced steel does not affect the anisotropy of mechanical properties, but rather increases the yield strength and ultimate tensile strength while maintaining high plasticity in the specimens. In specimens after ion-plasma nitriding, the fracture mechanism changes from initially ductile to a quasi-brittle fracture near the surface and ductile transgranular mode in the central parts of the specimens. The nitrided layer fractured in a transgranular brittle manner with the formation of quasi-cleavage facets and secondary cracks near the surface of the specimens. Brittle fracture of the compositional layer occurs due to the complex solid solution strengthening and particle hardening of austenite.