... *Nitrided+chromed+bimetallic alloy coating,spraying,welding *Bimetallic hardness:HRC58-72 *Durable Bimetallic coating screw Bimetallic coating screw barrelDiameter: Φ 15-Φ 300mmTechnical Data:Nitride Case ... .5mmChromium Coating Thickness 0.025~0.10mm Raw MaterialThe Finnished Product Processing Requirments38CrMoAla, SACM645Nitriding TreatmentCr12MoV, Cr12Alloy Steel38CrMoAla, SACM645,40Cr.AISI4140, ...