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Nitrogen pick‐up of steels through a plasma process
Author(s) -
Gammal Tarek El,
Yostos Badr,
El Sabbahy Fawzy Nagy
Publication year - 1992
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.199200507
Subject(s) - nitric acid , nitrogen , intergranular corrosion , metallurgy , materials science , nuclear chemistry , corrosion , oxalic acid , scanning electron microscope , analytical chemistry (journal) , chemistry , inorganic chemistry , composite material , chromatography , organic chemistry
Powdered austenitic steel (16/10/2 Cr/Ni/Mo) with nitrogen contents varying between 0.02 and 0.70 wt.% has been produced by the “Plasma Rotating Electrode Powder (PREP)” process from Cr/Ni/Mo steel rods. The nitrogen pick‐up was found to increase with decreasing particle size of the steel powder produced and with increasing partial pressure of nitrogen in the plasma gas up to a certain limit, beyond which no effect of could be observed. The effect of nitrogen content on the intergranular corrosion rate was investigated by exposure of the powder to 0.65 % nitric acid solution. The corrosion rate was found to increase with decreasing solution heat treatment temperature of the steel from 1100 to 1000°C and increasing nitric acid temperature from 95 to 126°C. Nitrogen was found to decrease the corrosion rates appreciably. The susceptibility of the tested steels to intergranular corrosion was investigated by scanning electron microscopy and by X‐ray scan spectra analysis after electrolytical etching in 10 % oxalic acid etch solution.