Showing papers by "U. Kamachi Mudali published in 1996"
TL;DR: In this article, Nitrogen-bearing types 304 and 316 stainless steels thermally aged at 823, 873 and 923 K for various durations were investigated to understand the relation between the sensitized microstructure (intergranular corrosion) and pitting corrosion resistance.
Abstract: Nitrogen-bearing types 304 and 316 stainless steels thermally aged at 823, 873 and 923 K for various durations were investigated to understand the relation between the sensitized microstructure (intergranular corrosion) and pitting corrosion resistance The sensitized microstructure was assessed as per ASTM A262 practice A (electrolytic etch test) and electrochemical potentiokinetic reactivation (EPR) tests; and pitting corrosion resistance was evaluated in an acidic chloride medium by potentiodynamic anodic polarization method The results indicated that the pitting resistance decreased as the degree of sesitization increased, and this was attributed to the formation of a heterogeneous microstructure consisting of Cr-rich M23C6 carbides, Cr-depleted regions and the carbide/matrix interfaces resulting from the sensitizing treatment Pitting attack was found at triple points, grain boundaries and precipitate/matrix interfaces Time-temperature-sensitization-pitting diagrams were developed for both the alloys based on the results, interrelating the sensitized microstructure and the pitting attack
40 citations
TL;DR: In this article, the IGC resistance of 304LN and 316LN stainless steels was assessed by ASTM A262 practice A test (electrolytic etch test) and electrochemical potentiodynamic reactivation (EPR) test.
Abstract: Intergranular corrosion (IGC) resistance of types 304LN and 316LN stainless steels (SS) thermally aged at 823, 873, and 923 K for various durations was assessed by ASTM A262 practice A test (electrolytic etch test) and electrochemical potentiodynamic reactivation (EPR) test. The results indicated that the type 316LN SS has significantly improved IGC resistance compared to 304LN SS. Based on the results of these tests, time-temperature-sensitization (TTS) diagrams were developed for both alloys. The secondary precipitates formed during thermal aging treatments were electrochemically extracted and analyzed by X-ray diffraction (XRD) to determine the types of precipitates formed during the aging treatments. The results indicated that the precipitates were mostly of M23C6 carbides.
37 citations
TL;DR: AISI types 304, 316 and 317 stainless steels (SS) containing various levels of nitrogen were evaluated for their pitting corrosion resistance in an acidic chloride medium containing 0.5M NaCl as discussed by the authors.
Abstract: AISI types 304, 316 and 317 stainless steels (SS) containing various levels of nitrogen were evaluated for their pitting corrosion resistance in an acidic chloride medium containing 0.5M NaCl and 0.5M H 2 S0 4 . Potentiodynamic anodic polarisation were conducted at room temperature to determine the critical pitting potentials of all the alloys, and the pit protection potentials of type 316 SS alloys. The pitted specimens were examined by optical microscopy and SEM. The results indicated that as the nitrogen content increased the critical pitting potentials increased, and the critical current density at the active to passive transition decreased indicating an improvement in the pitting resistance. Increase in nitrogen content in type 316 SS raised the pit protection potentials, and the potential range in which no new pits will initiate was also found to increase. The relationship between the critical pitting potentials and the nitrogen content was found using a nitrogen equivalent for molybdenum. Pitting attack was observed at triple points, grain boundaries, inclusions and at inclusion/matrix interfaces.
27 citations