[Carl n Susan]

It isn't quite clear what is broken but it doesn't really matter. A new axle is what you need.

You wrote about: welded on; hub; broken axle. I am guessing there is a problem with the spindle (aka hub) and not the axle tube itself. Your husband is correct, the spindle is welded to the axle tube. While it is possible to buy a replacement spindle, by the time you buy it, find someone qualified to cut off the old one and weld the new one on with the correct alignment, it is cheaper to just buy a replacement axle.

Replacement axles are available pretty much anywhere. Dexter, e-Trailer, most RV shops, and many trailer repair places can provide them and optionally install them for you.

You say the RV is in AZ and you are from NC so I don't know if you plan to do the work or not. Changing an axle is not overly complex if you are handy, physically capable, and have the tools needed. I had one changed in Jan. after destroying a spindle and it was around $800.