Welding hardened steel camshaft gears

[jagman]

I am hoping to repair the pitted gears on a steel camshaft by
mig welding. The gears are hardened but I am not sure if by
induction using a case hardening steel or by carburising and
heat treating. Is it feasible to use Mig, bearing in mind that
the gear is hardened? The drives are to distributor and oil pump
so the loading is not very high. I am more concerned with
reestablishing a flat surface which will maintain hydrodynamic
lubrication (without surface failure due to HAZ problems) than
reestablishing the original hardness although if this could be
achieved that would be very desirable. Can anyone suggest a
better method. I also have oxy acetylene.
Thanks for your help.
Regards Gus

 

[11echo]

Well... I'm reading between the lines here on a couple issues. If your thinking of using MIG welder, the damaged area on the cam must be small. You can forget about case hardening here, the case would ware thru in no time (too much continuous wear to stand up, if I understand the use). You could re-heat treat the cam, BUT you need to know exactly what the original metal is. My suggestion is to use a NI-CAD welding rod. The high nickel content in this rod makes the steel deposit very hard, kind of a pain to machine, but not impossible. And because of the hardness of this deposit, you wouldn't have to re-heat treat the work piece. My 2 cent! GOOD LUCK!

 

[GRoberts]

Another thing to consider, is machining/grinding the area to be welded undersized, the building up for re-machining. This way, if you choose a weld metal with the correct properties, you are ensured that you will be getting them uniformly all the way around the shaft, instead of possibly exposing part of the base metal/heat affected zone, which may or may not have the properties you want.