I wondered the same, probably just used for mould release or in this case forge release...

Not really sure, just a guess.
I was told from a reliable source that the A320 landing gear struts are made from 4340 forgings, they come in at 9000 lbs before machining and leave the plant weighing 1800 lbs.! That's allot of material removal!

pre hardened at 30 Rc then heat treated before finishing operations to 45 Rc
Pieces of art! I couldn't even imagine what they are worth apiece, my bet is north of a 1/4 million???