Dissimilar mechanical properties—microstructures microalloyed pipeline steels cracking performance under sour environment

The cracking behavior of an API 5L X52 microalloyed pipeline steel at 25 and 50 °C, under a sour environment, is compared with the cracking behavior of an API 5L X65 microalloyed pipeline steel with different microstructure and mechanical properties. The results show that the microstructure of X65 steel is much more resistant to develop and propagate a crack under proportional stress intensity factors and the same sour environmental conditions at room temperature (25 °C). The reverse result was obtained at 50 °C, however, a comparative growth in % criteria shows that X52 steel does not present a much better resistance to propagate a crack than X65 steel. These behaviors at both temperatures are indicative that steels microstructures might play an important role to resist cracking.