Study On Structure And Properties Of Ni-P/Nano Diamond Electroless Coating

Electroless plating technology is developing rapidly in recent years, there have appeareda number of multi-alloy plating, but Ni-P alloy coatings is still the most extensive applicationof composite coating with its high hardness, wear resistance, corrosion resistance and othercharacteristics of composite coating.In this experiment, Ni-P electroless coating and Ni-P/nanodiamond composite electrolesswere plated on steel material respectively, the effects of compound stabilizer concentration,bath temperature and pH value on electroless Ni-P deposit properties were studied to findsuitable bath in the preparation of Ni-P/nanodiamond composite coatings. The optimizedchemical bath in the addition of nanodiamond particles was plated on steel material usingelectroless plating technology in order to study the effect of nanodiamond concentration,stirring speed, temperature on the appearance, hardness, wear resistance, bond strength andother properties of composite coatings. On the base of specific experimental results, the effectof composite coating deposition process, heat treatment on the crystalline structure of coatingand the strengthening mechanism of post-treatment temperature on composite coatings wereanalyzed theoretically.Experimental results and theoretical analysis show that:(1)2.5~7.5ml/L stabilizer can inhibit the spontaneous decomposition of the bath, thehighest hardness can be achieved when2.5ml/L stabilizer was added.(2) When plating Ni-P electroless coating, the coating hardness was improved along withthe rising of pH value and temperature of the bath, and high density and even appearance canbe achieved. The adhesion of the coating and the steel were affected when ph value is over5.And high temperature is harmful to the stability of the bath. Through orthogonal analysis andverification, the parameters of the optimized electroless plating are: pH:5; temperature:85℃stabilizer concentration2.5ml/L.(3) The optimized chemical bath in the addition of Nanodiamond particles was plated onsteel material using electroless plating technology. Even surface appearance and size wereachieved when stirring speed was200r/min and nanodiamond concentration was10g/L. and the friction coefficient was smaller than other composite coating obtained under differentstirring speed and diamond concentration;(4) Spontaneous adjustment of the surface atoms of the coating was caused by heattreatment to Ni-P/nanodiamond composite electroless plating coating, and the coating wastransformed from amorphous state into crystalline state. And the Ni3P precipitation after heattreatment played the role of Dispersion strengthening, coating hardness was greatly improved.The optimal heat treatment process is400℃,1h.