Effect of crystallographic orientations on the hydrogen-induced cracking resistance improvement of API 5L X70 pipeline steel under various thermomechanical processing

• To suggest a thermomechanical treatment to improve hydrogen induced cracking resistance.
• Effect of different thermomechanical processing on microstructure changes.
• Effect of different thermomechanical processing on texture evolution.
• Effect of grain orientation on hydrogen induced cracking resistance.

In this study a thermomechanical processing was suggested to improve the hydrogen-induced cracking (HIC) resistance in X70 pipeline steel. Proposed thermomechanical treatment produced favorable crystallographic textures and significantly increased HIC resistance which is of great interest to petroleum industry. The results showed that the high angle grain boundaries and Kernel parameter values acted as hydrogen-trapping sites, leading to increased HIC susceptibility. Highest HIC resistance was obtained in sample rolled isothermally at 850 °C, due to the high proportion of grains oriented with {110} planes parallel to the normal direction and {111}//ND fibers accompanied by negligible fraction of grains oriented in {001}//ND.

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