Brittle fracture of metal stamped part

[Rnel]

I have a metal stamped part with two 90° bends. Material thickness is 0.070”, material type is S55C, heat treated (Austempered) to HRC 45. The part is then deburred and plated – Yellow Zinc per ASTM B633 Type 2, FeZn5. The part is experiencing brittle fracture through one of the 90° bends at 75% to 90% of its required load and 45% to 60% of its historic max load performance during testing. Should this part be baked for hydrogen embrittlement (375° F for 4 hours) or is that not necessary.
What steps would you take to root cause the problem.
I am doing this:
Analyzing material for carbon content
Researching heat treat process
Analysis for hydrogen embrittlement
Any and all help is appreciated.

RNel

 

[Metalguy]

Check the "grain direction"-should be 90 deg. to the bend.

It's usually a good idea to always bake out any H with steels this hard. Use 24 hr. at 375 deg F, not 4.

 

[CoryPad]

Steel with 45 HRC hardness MUST receive a post-plating heat treatment to reduce hydrogen embrittlement. For root cause analysis, you should examine a fracture face. If an intergranular pattern is present, then you likely have hydrogen emrittlement.


Regards,

Cory

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