Yes, black locust has strength and elasticity very similar to hickory. It's also rot resistant like cedar. And it has a coarse grain which grips the wedge well. I recall reading in the Foxfire books that black locust was often used for pegs to attach beams together in post & beam construction. Over the years the beams would rot away and the locust pegs would still be there, still hard and strong. Locust is the wood of choice for trail structures on the Appalachian Trail. In the NW it's considered an invasive species. I would have no qualms about taking a tree for axe handles. And any remaining wood would be great in the fireplace.