Effects of Trace Elements on Stress-Corrosion Cracking Of Austenitic Stainless Steels in Chloride Solutions

An investigation was made of the effect of some elements on the susceptibility of austenitic stainless steels to stress-corrosion cracking in boiling magnesium chloride solution. The steels were vacuum melted, of relatively high purity, and contained 20 percent nickel and 18 percent chromium. When there were no deliberate additions to the pure base composition, some 72 percent of the U-bend specimens tested cracked at an average time of 19 days. This is an impressive improvement over material of commercial purity. A number of additions were found that were detrimental and capable of causing cracking in 100 percent of the test specimens in a short time. These additions were nitrogen, phosphorus, arsenic, antimony, bismuth, ruthenium and aluminum. A number of other elements had no pronounced effect under the test conditions. Additions of carbon and silicon were beneficial. Alloys containing 0.10 percent carbon or 2 percent silicon and no other additions were completely resistant to cracking in tests lasting 30 days and longer. It is encouraging that austenitic stainless steels have been prepared by controlling the composition and purity which completely resist cracking in an aggressive medium at high stress levels for extended time periods. 3.7.2, 6.2.5, 3.5.8, 4.3.6.