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.
Why did the bearing/shaft wear?
How much is it worn?
Unless the worn shaft is round and cylindrical within 0.002" or so, and smoother than 20 micro inch rms or so, it is not suitable for re-use. Installing a bearing with ID machined undersize to achieve the desired clearance on an unsatisfactory journal won't buy much time.
The axial positioning of the bearing on the worn shaft will have to be done carefully. The bearing length may need to be shorter to prevent riding on an un-worn/larger portion of the shaft.
There are lots of details that need to be understood and controlled.
