Atom probe field ion microscope measurements of carbon segregation at an a:a grain boundary and service failures by intergranular stress corrosion cracking

This work reports on a critical measurement to understand the intergranular stress corrosion cracking (IGSCC) of pipeline steels: the atom probe field ion microscope (APFIM) measurement of the carbon concentration at a grain boundary (GB). The APFIM measurement was related to the microstructure and to IGSCC observations. The APFIM indicated that the GB carbon concentration of X70 was similar to 10 at% or less, which correlated with a high resistance to IGSCC for X70. (C) 2005 Elsevier Ltd. All rights reserved.

An evaluation of steels subjected to rock bolt SCC conditions

In order to understand the metallurgical influences on Rock Bolt SCC, an evaluation has been carried out on carbon, carbon + manganese, alloy and microalloyed steels subjected to the conditions previously identified as producing laboratory SCC similar to that observed for rock bolts in service. The approach has been to use the LIST test (Linearly increasing stress test) for samples exposed to a dilute pH 2.1-sulphate solution, as per our prior studies. SCC was evaluated from the decrease in tensile strength, ductility and fractography as revealed by SEM observation. A range of SCC susceptibilities was observed. Ten of these steels showed SCC, however there was no SCC for one carbon, two carbon + manganese and two alloy steels.