The chemistry of the failed fastener is the following:
C=0.36
Mn=0.73
P=0.015
S=0.006
Si=0.20
Cr=0.99
Ni=0.02
Mo=0.19
Cu=0.01
Fe=Rem
The chemistry of the good fastener is the following:
C=0.32
Mn=0.64
P=0.011
S=0.003
Si=0.16
Cr=0.99
Ni=0.09
Mo=0.20
Cu=0.14
Fe=Rem
kek78
Thanks everybody for their help. I think as CoryPad indicated I have some kind of Hydrogen Assisted Cracking going on. The source is unknown and without processing history I probably will never find out the source of it.
Purhaps these fasteners were plated then the plating removed to add the...
TVP,
The fasteners are clean of any signs of corrosion, SCC, pitting. Plus, if it was a corrosion problem, wouldn't the equipment (4 years in service) next to the failed equipment (6 months in service) have been susceptible to SCC also. This equipment is inside at a constant-dry temperature. I...
redpicker,
I have not got the results for chemistry yet, but it is getting done. The microstructure looked typical, nothing out of the ordinary except for the large crack across the cross sectional area of the fastener with the prior austenite grains falling apart and micro cracks following...
swall,
These fasteners are in a piece of equipment (they just hold it together) indoors at 65 F. Also, another piece of equipment (the same design) is right next to it and has been in service for 4 years without any failures. No corrosion by-products are seen in any of the fasteners or...
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...
