TIG welding case hardening steel

[TeoAlfa]

I have a project of welding some 17NiCrMo6-4 (AISI4317?) steel.
The idea is to weld a motorcycle engine sprocket to a machined bar of annealed 17NiCrMo6-4 steel.
Problem is that it's difficult to manufacture the internal spline on the bar itself, so we get the ready made spline from the sprocket and weld it on the annealed bar.
The sprocket is case hardened. I will machine the teeth of the sprocket on the lathe and also i will make a chamfer for the weld. Look at the attached CAD image to see what the sprocket will be like after machining.

Yellow areas are untouched/hardened areas and red are the machined areas.

Next we will get the bar and machine it in the shape you see in the attached CAD image (adaptor-silver part).

The two will fit together and will be welded all the way round, like this:

Of course i will preheat the assembly @300degC prior starting welding it.

1) Do you think i can weld the 2 parts without annealing the sprocket?
I assume that the machined areas of the sprocket (red areas) will unveil the "soft" core of the sprocket so i will be able to weld the two with success.

2) Do you think that i can make a decent stress relief treatment by putting the welded assembly in a simple oven for 6 hours at 160 deg.C ? That was the reccomendation of a local heat treatment shop.
But i read that 17NiCrMo6-4 needs to be stress relieved at 630-650 degC.

3) Finally, what type of filler rods do you recommend me to use? ER80S-D2?

 

[mfgenggear]

Ok looking at the 1/2 view detail below , it appears there will be welding on adjacent case hardened area. is that correct?
if so it will not work well, on case harden parts, did you specify what the core hardness is? is it 50 min?. the areas welded will work if it is not case harden the core hardness is low enough. and even then it take a special weld schedule. may be some one here can help with that . if the case is carburize, the best option might be to induction harden the outer diameter of the sprocket except quench it to retain a low case hardness in that area. I made some parts years ago the weld areas were aisi 9310, and was core hardened only to 33-43 HRc, except with electron beam welded. but some parts had failed NDT. barely made the order.

 

[Tmoose]

As I recall, before the image links broke, it looked to me like there were some bores that might house bearings etc.
Maintaining excellent concentricity after welding is a non-trivial task.