Study Of Effect Mechanism Of W On Crystallization And Properties Of Electroless Ni-P Based Alloys

Due to excellent physical, chemical and mechanical properties, electroless platingNi-P alloy coating has a very wide range of industrial applications. Heat treatment caneffectively improve the hardness and wear resistance of electroless plating Ni-P alloycoating. With the rapid development of science and technology, electroless platingNi-P alloy coating can no longer meet the requirements, in some areas such as wearresistance, corrosion resistance, heat and electromagnetic performance. In recent yearsthe rapid development of more excellent of electroless Ni-based ternary alloy andcomposite coatings has great progress. The addition of third element in the Ni-Pelectroless plating can improve the hardness and wear resistance.This paper focuses on the effect of W on the chemically deposited Ni-P basedalloy layer structure, surface morphology and the heat treatment, hardness, corrosionresistance and wear resistance. And two alloy coating heat treatment the degree ofcrystallization, grain sizeimpact, corrosion, wear mechanisms were compared. Duringthe test, the morphology and composition analysis using scanning electron microscopyand energy dispersive spectroscopy, XRD quantitative analysis of W codeposition ofNi-P based alloy coating heat treatment the degree of crystallization, grain size, withimmersion test coating corrosion, wear, experiment to study the mechanism of coatingperformance by microhardness testing. The following conclusions can be drawn:（1） The Ni-5.13%W-9.32%P and Ni-9.27%P alloy coating using chemicaldeposition has amorphous structure, and the P content of these two coatings are thesame （similar）, W deposition plated coating of crystaldegree.（2） In heat treatment under the same temperature the degree of crystallization ofthe Ni-WP alloy coating is higher than the Ni-P alloy coating, and the proportion ofcrystallization in the crystallization of Ni is much larger than the proportion of Ni₃Pphase crystallization of Ni-WP alloy. The reaction temperature of coatingcrystallineprecipitate Ni₃P is400°C, while the precipitation of Ni-P alloy plating Ni₃P thecrystallization reaction temperature is300°C. At this temperature, two alloy coating arenot full crystallization, and the presence of W accelerate heat treatment coatingof Ni inthe crystallization process, and improve the reaction temperature of Ni₃Pcrystallization.（3） The micro-hardness in the coating before and after heat treatment is determined by the degree of crystallization of the coating, Ni and Ni₃P a considerablenumber and grain size. The hardness value of plated Ni-WP is larger than the Ni-Pcoating, which is due to W, Ni-WP plating reasons for the high degree ofcrystallization. The solid solution of W in the Ni reduce the size of Ni₃P hinder thegrowth of the Ni phase, so that the hardness of the Ni-WP is higher than the same orsimilar P content Ni-P coating.（4） Plated and200°C low temperature heat treatment, no change in the latticestructure, the corrosion resistance of Ni-P coating can be slightly higher than theNi-W-P plating. After200℃, with the heat treatment temperature, the corrosionresistance of the two alloy coating first decreased and then increased corrosionresistance than plated corrosion resistance of Ni-W-P plating alloy after heat treatmentat700℃, the whole, due to refinement of the coating alloy of W, and make theorganization more dense, making the Ni-WP coating alloy corrosion resistance than thealloys of Ni-P coating.（5） Plated and low temperature heat treatment, Ni-P coating wear rate of Ni-WPcoating. After400℃heat treatment, both the hardness is highest and the lowest wearrate with the hardness of the coating of heat treatment temperature decreased, the wearrate increases, but the Ni-W-P coating wear resistance superior to the Ni-P coating.Before and after heat treatment, Ni-P coating wear in the form of adhesive wear; platedand low temperature heat treatment of Ni-WP coating wear form of adhesive wearbehavior, wear the form of micro-cutting wear mechanism in high temperature heattreatment （600°C and above）. W codeposition improve the wear resistance of the alloycoating.