originally posted Fall 2002.
I recently processed a job through our shot peen department that had a conflict in specifications. If someonw could shed some light on this, I would greatly appreciate it.
The parts were Pivot Pins for a medium to small aircraft. They were made of 4130 steel, heat treated to 200-220 KSI. The processing included shot peen, followed by Electroless Nickel Plating.
The plating spec called baking at 350°F for 4 hours for Hydrogen Embrittlement relief, followed by 725-750°F for one hour to harden the nickel.
The peening spec prohibits baking above 475°F, while the plating spec requires shot peen and post-plate heat treatments.
My first thought was that the shot peen should not be rquired since the heat treat to cure the nickel would erase the effect of peening. Because the plating spec clearly required both peening and baking, the parts were processed through all steps.
My question is, "Why does the plating spec require peening if the post-plate cure exceeds the shot peen specification's temperature limitation?"
The parts were plated in accordance with MIL-C-26074E, and peened in accordance with AMS-S-13165.
Thanks for your input.
jlewis@swunited.com[This message has been edited by webmaster (edited April 21, 2003).]
