"8740 Steel Fasteners"

Question:

"We have 8740 steel fasteners 160,000psi, RC36-40. A plating company they were sent to did not bake the parts. We found the lack of a bake certification in the paperwork. If we have the pieces re-done properly with a recomended 23 hour pre bake instead of the 3-4 hour pre bake what is the likelyhood of them being hydrogen free after the second time? The spec is Cad 2 Type 2 QQP416 yellow w/bake."

Answer:

The issue of baking parts after plating is involved as the plating does not allow the hydrogen to be driven from the material. There is some evidence that the hydrogen is driven to non-mobile traps during post-plating baking; therefore unavailable for causing damage during subsequent stressing. A 3-4 hour bake at ~400F has been described as in literature. For additional information regarding baking times and temperatures, please refer to several ASTM Standards discussing plating and hydrogen embrittlement.

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