| Abstract: | ![]()
Amplified discussion of the influence of Silicon and Molybdenum on the stress corrosion cracking proneness of austenitic and austeno-ferritic chrome-nickel steels Tests have been carried out in boiling magnesium chloride, calcium chloride, NaCl, water (150–200°C) and hot steam (500°C); in the two last-named cases, the tests were carried out with and without the addition of chloride and oxygen. The following materials were tested: steels with (per cent.) 17 and 17.5 Cr, 12–15.5 Ni, 0 and 2.5 Mo, 0 and 4 Si, less than 0.03 C, as well as steels with 20 and 21 Cr, 8—10 Ni, 0 and 2.5 Mo, 0 and 3 Si, 0, 1.5 CU, less than 0.05 C. Silicon has a favourable effect on the stress corrosion cracking behaviour in magnesium chloride and also in calcium chloride, but a detrimental effect in NaCl and water. Its probable effect is to inhibit the extension of the crack by crystallographic obstacles and, later, by the formation of a surface film of poor conductivity (where Mo also plays a part). The attempt is made to interpret this behaviour on the strength of electro-chemical investigations; in this connection, renewed critical reservations are made in respect of the test in magnesium chloride. |
