kek78
Materials
- Jun 19, 2007
- 6
I have several failed fasteners. After metallurgical evaluation the failure mode is classical grain boundary embrittlement (rock candy fracture surface, cracks along prior austenite grain boundaries in micro). Hydrogen embrittlement, right? However, these fasteners were not plated (cad, zinc, etc.), they only have a black oxidized coating. I would not think this type of coating process would be a source for hydrogen pick-up. Could this be temper embrittlement? The hardness on these fasteners are Rc 44 and they were in service around 4-6 months. The material appears to be clean from the micro (no massive inclusions). Any suggestions? Thanks