... frequency-changing. Main parts:Pump body:(material used: HT250)Fluid cylinder body: (material used: 304ss,316ss,316L ss,1Cr18Ni9Ti, 420ss ... applied to prevent fatigue crack.Crank shaft (material used: 35CrMo, 4140,1045,QT800)Nitrogen hardening treatment is ... hardness, durable and corrosion resistant feature.Plunger (material used: superior ceramic, Colmonoy coated,Tungsten carbide coated wear ...