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Hydrogen embrittlement suspicion
2003
Q. Piston rod of 1045 steel d=18 mm, l=30 cm should follow the sequences as below:
1- first grinding
2- surface induction hardening depth=1mm
3- cracks detection
4- tempering microhardness at this stage 450 HV (300 gr load)at o.6-1.0 mm depth area.
5- grinding
6- hard chromium micro cracked type 25 micron.
7- last buffing 5 micron
THE QUESTION IS : SHOULD WE EXPECT HYDROGEN EMBRITTLEMENT AND NEED FOR BAKING? The expert assistance will be appreciated.
Hadi Khosravi- Tehran, Iran
A. Hadi, if it were my part, I would bake it. 150 °C, for 4 hours, within 4 hours of plating.
Lee Gearhart
metallurgist - E. Aurora, New York
2003
Q. Dear Lee,
Thank you for responding. I received different answers, the most interesting was by Mr. Guffie through his book :
Handbook of Hard Chromium Plating.
on page 84 as follows: above 35 rockwell baking required for deposit thicker than 0.001 inch. In our line I am exactly sticking the borderline 0.001" or 25 micron. That is why I need more experienced answer. Hoping get rid of baking facility for 3000 shaft per day.
Sorry for late response,
Hadi Khosravi [returning]- Tehran, Iran
2003
A. Hi Hadi. Although I'm not privy to Guffie's thought process, I'd go with Lee's suggestion regardless of that thickness clause. If you do thousands of shafts per day and there is no evidence of embrittlement at all, it might be different. But unless you have overwhelming evidence of freedom from embrittlement, I would agree with Lee and wouldn't mass produce a chrome plated hardened steel part without hydrogen embrittlement relief.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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