material choice for chainring adapter?

[MPP]

I designed an adapter for a bicycle chainring which allows the use of a certain size chainring with a certain style of crank. It will be subjected to high stresses. Decided to go with steel over aluminum for strength but am unfamiliar with steel grades. According to the software 1008 or 1018 look to be the best available option, does this sound correct?
Also, I'd like to have the part powder coated, but am concerned about the possible need for heat treament before this step, so I may have to have PC done aftwards. Knowing the material I am looking at and it's intended application, does it sound like I may need to have the part heat treated before PC? Any recommendations?