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Brittle fracture of metal stamped part

Brittle fracture of metal stamped part

Brittle fracture of metal stamped part

(OP)
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

RE: Brittle fracture of metal stamped part

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.

RE: Brittle fracture of metal stamped part

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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