View Sample Alloy Digest Data Sheet (PDF)Since 1952, Alloy Digest has been the leading reference for materials property data on metals and alloys used throughout the world. Featuring graphs, charts and tables, these sheets give facts and figures on composition or characterization, physical and mechanical properties, heat treatment, and machinability.SURF HARD is a nitriding alloy steel designed for those applications requiring exceptionally hard wear resistant surface and a tough core, such as heavy duty gears, spline shafts, rubber and paper mill rolls, cylinder liners, etc.