A method of thermo-mechanically processing a preform composed of tool steel and a tool to modify a workpiece. The preform has a region containing austenite. The method comprises establishing the region at a process temperature between a martensitic start temperature and a stable austenitic temperature. While at the process temperature, the region is deformed to change an outer dimension and to modify the microstructure to a depth of 1 millimeter or more. The tool comprises a member composed of tool steel. The member includes a first region that extends from the outer surface to a depth of greater than 1 millimeter and a second region. The first region includes a plurality of grains having an average misorientation angle greater than about 34°, an average grain size that is at least 10% smaller than the second region, and has a different grain orientation than the second region.