You have not provided much to go on.
You have not said what the shaft is made of.
I assume it is some flavor of steel.
Welding worn shaft bearing journals brings on big risks from poor metallurgy, material integrity ( cracks etc) and compromised geometry (undercuts, loss of fillet radiuses, and more).
Distortion/bending of the shaft is practically guaranteed.
The welded shaft journal needs to re-machined to be round and very smooth.
You have not said what the bearing "shell" is made of.
I assume it is a babbit lined insert. I believe "welding" the babbit on an insert brings the risk of damaging the bond between steel lacking and the babbit material. The required roundness, size and finish requires re-machining of the babbited Inside Diameter too.
If the bearing insert is solid bronze, adding material by welding will likely distort the bearing insert too.