Hardening Stainless Steel

http://www.askzn.co.za/tech/tech_grades.htm

316 is a bit harder....and then kolsterising the 304 or 316....then maybe 440c and then A286...

short of work hardening, no, there is not. if you use a martensitic stainless (420, 440) then yes, you can heat treat it. If you use a precipitation hardening stainless (15-5, 17-4PH, A286) you can precipitation harden it. but 300 series stainlesses are not heat treatable. Problem is, that the heat treatable alloys are not terribly easy to weld (420 is weldable if the welder knows his business, the others, eh, not so much.) you could try a duplex alloy like sandvik 2205 or 2507 which are weldable (but with some difficulty) and have higher yield strengths than the 300 series and have superior corrosion resistance but are not heat treatable. typically heat treatability/hardenability and weldability are inverses of each other.

I will say that you CAN salt bath nitrocarburize (Kolene's QPQ process or equivalent) the stainless parts and obtain a high surface hardness which may be enough to solve your problem. but the depth of hardness will be measured in tens or hundreds of microns at most. and it will have a somewhat detrimental effect on corrosion resistance.

Personally I would rethink the approach. If it were me I would make the parts like this:

1. Use 25mm bar and in the lathe use a rota-broach to cut the 8mm socket and part to length.
2. Hold part in 25mm collet and turn pin on the end of the part.
3. Use an emergency collet and mill a 25mm diameter, offset to center line and use that to turn the 16mm diameter.

The time and money saved by not welding will pay for the rota-broach. You are not shackled to using only weldable material. For the stainless I would use 17-4PH and I would use Fatigue-Proof for the steel. Both materials will greatly reduce the wear on the socket head.

Rotary Broach web site: http://www.slatertools.com/?gclid=CMj6grH0vrACFaVdTAodv09HCw

Thank you all for your help, I conclude:

• There is no easy way to harden 304 or 316, although it can be work hardened, nitrocarburized or kolsterised.
• Hardenability and weldability don't occur in the same stainless, at the moment they are a dream to weld and I would prefer not to complicate that.
• Machining them from solid is tooooo expensive, I've checked. Currently there is virtually no machining, even the 8mm with the Circlip groove is pressed in.
• Possibly laser cutting an 8mm hole and punching the hexagon may help.

Thank you all again, Tony