Influence of test method and relaxation on the result from stress corrosion cracking tests of stainless steels in dilute neutral chlorides
2003 (English)In: Corrosion, ISSN 0010-9312, Vol. 59, no 9, 828-835 p.Article in journal (Refereed) Published
Recently, as a part in the European Carbon and Steel Community (ECSC) project "SCC of newer SS grades" (NEWSCC), a u-bend test program in neutral dilute chlorides was performed. Earlier presented data of stress corrosion resistance on stainless steel (SS) in the same environment have been based mostly on constant load testing. The results from these two test programs differed, even though they were performed at the same environmental conditions and in the same equipment. The ranking of alloys inside the two material groups of austenitic and duplex SS was not changed. But, the ranking between the groups was changed. In the constant strain test program with u-bends, the austenitic SS received better results compared to the duplex SS, compared to the previously performed constant load test program. Another result was that AISI 304L (UNS S30403) steel experienced cracking first at a temperature as high as 125degreesC in 1% chloride solution. Experiences from service have given a maximum service temperature between 40degreesC and 60degreesC. Mechanical testing including relaxation tests at actual testing temperature was done to evaluate the differences. The austenitic SS experienced up to 30% relaxation but the higher alloyed duplex steels only similar to10%. The differences in relaxation behavior must be considered during evaluation of u-bend test programs. The degree of high relaxation of AISI 304L also might explain the improvement for u-bend specimens compared to constant load test data and service experience. The difference in relaxation behavior is also important when a test method shall be chosen for simulating practical experience. For example, constant strain samples such as u-bends are the most representative for conditions where a strain causes the load (for instance, in nonstress-relieved bent heat exchanger tubing). However, the huge difference in relaxation for different SS in a u-bend will not give representative results for a constant load application (for instance, stress-relieved heat exchanger tubing or pressure vessels).
Place, publisher, year, edition, pages
2003. Vol. 59, no 9, 828-835 p.
constant load, relaxation, stainless steels, stress corrosion cracking, u-bends
IdentifiersURN: urn:nbn:se:kth:diva-13437ISI: 000185308400010OAI: oai:DiVA.org:kth-13437DiVA: diva2:325350