From the pictures,..it looks like someone attempted a weld repair......?
That appears to be CI and Yes it can be fixed. Nickel rod will work just fine. You could also have it brazed but it would show up as a brass color.
Take it to a good welder that is qualified to repair cast iron. I belong to a machinery forum and there are at least 1-2 posts a week on repairing broken parts or casts from CI woodworking machinery. I had a repair that I needed for a machine and I must say. My welder told me that the repair would be stronger than the cast- they did a fantastic job.
It will Probably be $75.00 -$100.00 (give or take a few dollars )to have that fixed. Just don't use brazing - it will stand out . If they use nickel and build it up , they, or you, can shape it down to its original profile with a hand held grinding wheel and then sanding disk. There is also a liquid you can buy to tarnish the metal once the repair is completed to blend in with the aging of the bench. I just don't remember what it was called.
Best of luck,