Study Of Influence Mechanism Of Crystallization And Performances Of Electroless Ni-W-P Coatings With High Phosphorus Contents

In this paper, the microstructure characteristics (including the degree of depositionlayer crystallization, phase transition, grain size and residual stress andlattice evolution of the contingency) of two high phosphorus Ni-W-P alloy coatings ofdifferent phosphorus content before and after crystallization with heat treatment werequantitatively analyzed by XRD, to reveal the chemical deposition of high phosphoruscontent of Ni-W-P coatings of nana-technology and the nature of the deposition layehardness, in order to explore the high phosphorus content of Ni-W-P alloy depositionlayer abrasion resistance and corrosion resistance mechanism.The results showed that:(1) By adjusting content of each component of deposit liquid to obtain twosediment layers in high phosphorus content, the components of the two sediment layersrespectively are Ni-3.88%W-13.36%P and Ni-4.06%W-11.34%P, which both belongto the amorphous structure.The amorphous degree of the high phosphorus depositedlayer is higher and the surface morphology of plating condition is denser,however,there are some holes in the surface of the relatively low phosphorus deposited layer.(2) When the temperature of heat treatment crystallization is below400℃, onlythe Ni phase crystallizes;Up to400℃, except the Ni phase, they are beginning tohappen Ni3P crystal separation;increasing to700℃, the crystallization degree ofdeposited layers continuously improves, but not fully crystallized. Below400℃, thevolume fraction of Ni3P phase of two coatings were higher than that of Ni phase;however,when the temperature is higher than400℃, the volume fraction of Ni phasein the relatively low phosphorus deposited layer is in turn higher than Ni3P phase,while the volume fraction of Ni3P phase in the relatively high phosphorus depositedlayer is always greater than Ni phase. During continuous heating crystallizationprocess, deposition of a layer of cellular became smooth.(3) After the crystallization heat treatment temperature increases, and Ni3P phaseNi grain size increase, in400℃and500℃temperature, the two, both present Ni3Psediments in grain size is greater than the Ni; More than500℃, two phase the size ofthe opposite. High phosphorus content of sedimentary two phase grain sizesignificantly less than p content low sedimentary grain size, attributed to the formermore than the latter Ni3P phase in the river dispersion exhalation, effectively preventthe Ni phase to grow up.(4) Along with the crystallization heat treatment temperature increases, the hardness of sedimentary increase, all in500℃maximum when, temperature higherthan500℃, hardness began to drop, but high phosphorus content of sedimentary speeddown relatively slowly, the main and sedimentary two phase of the grain size and thenumber of Ni3P is concerned.(5) The minimum wear rate of the two coatings both appears at500℃of heattreatment crystallization temperature. With the temperature increasing, wear rateincreases.But in Ni3P precipitation under temperature, high phosphorus content ofcoating has better abrasion resistance. The wear resistance of the coating are mainlyaffected by its grain size, residual stress, the crystallization degree and coating holefactors. With state and low temperature heat treatment crystallization, two coating thewear behavior, both present gelling wear, and high temperature heat treatmentcrystallization, coating to play a leading role in the form of the wear and tear of microcutting wear mechanism.(6) Soaked in sulfuric acid solution the two coatings occurs maximum corrosionrate at400℃, while the high phosphorus coating has better corrosion resistance. Thetwo coatings both exhibit uniform corrosion characteristics.