A series of iron-chromium-nickel alloys was melted under a nitrogen atmosphere at several different pressures. Nitrogen-high pressure melting (N-HPM) was conducted under pressures ranging from 0.1 to 200 MPa. The total nitrogen concentrations achieved in these alloys were proportional to the square root of the nitrogen pressure used during melting. Nitrogen took the form of soluble interstitial nitrogen and metal nitride precipitates, Fe^N and CrN. Tensile properties of N-HPM alloys were directly proportional to the nitrogen concentration in the alloy.
It is well known that mechanical properties of commercial stainless steel are improved by alloying with nitrogen. In this study a series of nitrogenated commercial 201 stainless steel alloys with nitrogen levels as high as 2.6 wt. % were obtained by melting in a hot-isostatic-pressure furnace using nitrogen as the pressurizing gas. Nitrogen concentrations in excess of 1.25 wt. % formed a series of different chromium nitride precipitates and morphologies depending upon the nitrogen concentration. Five different nitrogen levels were fabricated using the same processing conditions recommended for 201 stainless steel including hot-and cold-working, and heat-treating at two different temperatures. Tensile strength of the nitrogenated materials at each processing step was related to the interstitial nitrogen concentration and the presence or absence of precipitates. The presence of chromium precipitates did reduce the fracture ductility and changed the fracture features. This U.S. Bureau of Mines study shows that increasing the nitrogen concentration in commercial steels above their current level has positive effects on mechanical properties as long as the nitrogen solubility level is not exceeded and chromium nitride precipitates begin to form.
Thick chromium deposits were prepared by the electrolysis of aqueous chromic acid baths. Metal containing 0.005% oxygen, less than 0.002% nitrogen, and only traces of metallic impurities was obtained upon electrolysis of purified solutions at elevated temperatures. After consumable electrode arc‐melting, this type of chromium could be hot‐worked to rod and drawn to wire that was ductile at room temperature.
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