Material Recomended Core Hardness Plasma Nitride Surface Hardness Total Case Depth (Inches) 1020, 1045, Cast Iron 14-18 File Hard 0.0005" 0.002-0.010 8620, 9310, 9315, P6 14-18 52-58 0.012-0.028 4130, 4140 28-32 52-58 0.008-0.024 4340 28-32 49-55 0.008-0.024 P20 28-36 57-62 0.008-0.020 Nitralloy 135 M 28-36 67-71 0.008-0.020 A2 54-56 65-70 0.005-0.010 D2, D4, D6 57-59 65-70 0.005-0.010 H13, S7 45-50 67-71 0.004-0.012 M2, M42, ASP 60-65 69-72 0.0005-0.002 304, 316 S.S. 0 62-66 0.002-0.008 15-5, 17-4, PH SS 31-38 62-66 0.002-0.008 429, 436, S.S. 24-38 68-70 0.004-0.008