Dissertation > Industrial Technology > Chemical Industry > Electrochemical industries > Electroplating industry

Preparation and Characterization of Ni-W Alloy and Ni-W/ T-1 Composite Coatings

Author SuZhiJiang
Tutor WangWei
School Tianjin University
Course Applied Chemistry
Keywords Ni-W alloy Ni-W/T-1 composite electrodeposition hardness wear resistance
Type Master's thesis
Year 2009
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Hard-chromium has been used widely in industry for the excellent hardness and wear resistance. To preparing coatings which can replace hard-chromium has attract considerable interest for the increasing attention on environment. In this thesis the preparation, characterization and properties of electrodepositing Ni-W alloy and Ni-W/T-1 composite is studied in a electrolyte system without pollution in order to obtain coatings with high hardness, abrasive resistance and corrosion resistance. EDS, ESEM and XRD techniques are used to investigate the composition, surface and structure of coatings. The properties of coatings are tested by hardness-tester, abrasive tester and electrochemical measuring system. The factors how to influence the properties of coating is also discussed.It is researched that the influence of electrodeposition parameters on the electrodeposition speed, composition, structure, surface and hardness through the study of citric system Ni-W alloy technology and the mechanism was analysed. The results show that: additive C-2 has a effect of increasing the current efficiency greatly and sodium citrate can smooth the surface of the planting while increase the hardness at the same time. The optimal technology was got through orthogonal experiment, in which condition Ni4W alloy was prepared. The coating prepared in optimal condition with metal white appearance, 680HV hardness and small inner stress is excellent.The negative process has the effect of avoiding hydrogen brittleness and minishing inner stress. However the atomic fraction of W will be low to some extend. Companies with the increase of Na2WO4 concentration the electrodeposition speed become slow obviously, the atomic fraction of W increase gradually and the inner stress becomes higher. According to the XRD testing, increasing of the W content is propitious to the minishing of the grain size and can make the surface smoother.It is researched that the influence of electrodeposition parameters on the electrodeposition speed, composition, structure, appearance and hardness through the study of acid non-complexant system Ni-W/T-1 composite technology and the mechanism was analysed. Companies with the increasing of T-1 concentration, mass fraction of T-1 in the coating increases simultaneously and then will decrease a little. So there will be a best condition for the composite coating in hardness and wear resistance. What is more, the T-1 particulate and Na2WO4 have an effect of inhibiting each other. Compare with the watt Ni and Ni-W alloy, the stable polarization curve of composite coating move to the positive potential, so the corrosion resistance of composite coating is the best.

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