Gear segment welded to shaft

Hello , I have a Wheel Horse Lawn Tractor , I have the need to replace a half moon gear segment that is welded to a 3/4 in. shaft , the gear appears to be a steel casting and was either Stick or MIG welded to the 3/4 cold rolled shaft , I checked the original weld fillet and it's as hard a diamond and the gear is likewise hard up to approx. 1/16 " from the weld line , I will probably not try to remove the old gear , will just make a new assembly and incorporate the new gear into this , I have been an Aircraft / Aerospace welder/weldor most of my working career , mostly GTAW and Electron Beam , am real curious as to what filler material was used that is as hard as a "Rock" to join a gear and shaft assembly , I may just go with Silver Braze . Thanks Phil L EAA 12873