Abstract:
Electroplating of nickel-tungsten alloys on mild steel for wear resistance improvement was studied.Sulphate plating bath was selected for the alloys. Effects of plating parametes on Taber Wear Index(TWI) were investigated. The plating parameters were current density, plating time, temperature,pH, concentration of complexing agent, and concentration of sodium tungstate. Optimum platingbath conditions considering the greatest values of wear resistance (the lowest TWI) with no crack onsurface were obtained using gradient search technique at constant pH of 5 and controlled thicknessof 10 ?m. The optimum conditions were current density of 4 A/dm2, temperature of 35 0C,concentration of complexing agent of 105 g/l, and concentration of sodium tungstate of 10 g/l.These conditions yielded the lowest TWI of 14.5 ? 0.21 and the greatest microhardness value of667.2 g/mm2. Grain size of coated surface and tungsten content in coating were found to determinethe wear resistance. The smaller the grain size and the higher the tungsten content in coating, thegreater the wear resistance was.