The Corrosion Resistance of Sintered Austenitic Stainless Steel
It is shown that the resistance to corrosion by sodium chloride solutions of sintered austenitic stainless steel is dependent upon the type of sintering atmosphere employed. While sintering in vacuo always gives corrosion-resistant specimens, sintering in dissociated ammonia or hydrogen can lead to loss of corrosion resistance. Sintering in dissociated ammonia is shown to result in considerable absorption of nitrogen in the temperature range 700–1000°C. The nitrogen is desorbed above 1000°C., but absorption again occurs during slow cooling. Loss of corrosion resistance is due to the formation of chromium nitride which results in localized chromium depletion of the matrix. Cooling at 200°C/min from the sintering temperature prevents nitrogen absorption and maintains corrosion resistance. The water-vapor content of the sintering atmosphere also influences the degree of corrosion resistance. Specimens sintered in hydrogen were corrosion-resistant only when the water-vapor content was below 50 ppm.
KeywordsCorrosion Resistance Austenitic Stainless Steel Corrosion Test Sodium Chloride Solution Crevice Corrosion
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