Fracture Mechanism and Countermeasure of Cylinder Cover Bolt in a Make-up Hydrogen Compressor

The cylinder cover bolt of a make-up hydrogen compressor in an enterprise suddenly fractured. Combined with the thread processing technology, a series of analyses were conducted on the cracked bolt, including macro morphology observation, chemical composition analyses, microstructural examination and micro morphology observation. The results showed that, due to the large number of inclusions inside the bolt material and thread surface, microcracks on the thread surface were generated during the thread machining process. The bolt final fracture was due fatigue extension of microcracks in root to caused by alternate stress.