Yep, good choice, likely not brazing, brazing usually shows signs of melted brass - or some form of yellow filler metal. Yours looks like somebody used welding heat to melt themcasting. So if you take it off, you’ve got next to irreparable melting in the spindle and ID surface of the gear. Also, rule of thumb: brazing adheres to the surface with bronze or brass filler. Welding melts the surface and fills into the melt with welding rod of some sort. Welding is a fusion of materials, brazing, more like ”glue” on the surface...
Better off to just do some chip making and see how it runs. If it’s good and can hold to a thou repeatedly, when turning round stock, enjoy it and use it,..
If it needs repair, well then dig in. Recommend you find replacement spindle parts before you tear down. Then just figure on throwing the welded bits away and replacing with newer, better components.