17-4 ph vrs 303

[Harold_V]

I have no experience with 420, so I hesitate to comment. I do have limited experience with both 410 and 440C, neither of which did I enjoy machining. The 410 was in the annealed state and gummy, while 440C is just plain tough to machine. To its credit, it machines with a very nice surface finish, however, unlike annealed 410.

Passivation has little to do with corrosion resistance. Its purpose is to remove free iron from the surface of stainless, iron that yields superficial rusting that is unrelated to the base material, which usually does not corrode by rusting. Said another way, a piece of 303 won't rust, but it can experience surface rusting if it hasn't been passivated. It isn't the base material that rusts, but contamination that has been created by exposure to iron. Indications are, from your comments, that passivation isn't required for your application.

H

edit:
I was just thinking. If you choose to move to a 400 series material, you might explore 416. It is the 400 series equivalent of 303. It is the best machining of all the stainless materials and can be heat treated if necessary. Machines with a very nice surface, typical of most stainless materials. I suspect that the plate made from 416 would perform equally to one made from 303, if not better. Heat treating would improve performance, but likely a little beyond your home shop capability to execute. I have no experience with heat treating 416.

[partime]

I agree with Harold on all fronts. If you like 303 you will love 416. I believe 416 can be hardened to around RC35 perhaps as high as 40? But don't quote me on that.
I have never machined 420 that recall so can offer you nothing there.

[RSG]

Thanks guys!

I have some time so I will investigate 416 and 420. For now I'm testing the 303 to see how well it wears. Never know, it might be ok itself since these parts don't get used a whole lot.