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Electro-deposition Processes, Microstructures and Properties of Ni-P & (Ni-P)-SiC Coatings

Author: ShaoGuangJie
Tutor: YaoMei
School: Yanshan University
Course: Materials Science
Keywords: Ni-P alloy Electrodeposition Organizational structure Coating Performance Rare earths Ni - P - SiC composite coating Centrifugal force field Electrochemical Behavior Deposition process
CLC: TQ153
Type: PhD thesis
Year: 2002
Downloads: 599
Quote: 4
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Abstract

Electrodeposited Ni-P alloy coating has excellent performance in recent years has been widely appreciated. Electrodeposition process on the basis of success of the industrial production value of the early stages of the electrodeposited Ni-P alloy deposition behavior, organizational structure, corrosion and wear resistance system. The same time, the power of rare earth elements in the deposition of Ni-P alloy process more in-depth discussion. This paper presents a high-speed electro-deposition method in a centrifugal force field, and centrifugal electro-deposition (Ni-P)-SiC composite coatings influencing factors and coating properties were studied. Cathodic polarization curves and cyclic voltammetry to study the electrochemical behavior of various additives in the Ni-P alloy plating electrodeposition process. Comprehensive analysis of the experimental results, the bath recipe (containing the FM additive as the main complexing agent, and 2 g / L of rare earth chloride) and process conditions, can get good quality low phosphorus in phosphorus and high phosphorus coating . Initial deposition behavior of electrodeposited Ni-P alloy coating were studied. Found that the initial deposition behavior of electrodeposited Ni-P alloy by the matrix material organization. 45 annealed steel surface, since the pearlite structure containing cementite phase and having a relatively high density of grain boundaries, and thus the deposition of the initial coating priority here nucleation and growth; coating on the substrate surface is a nano-scale crystal particles gathered together to form a poly-crystalline forms exist. With the extension of the plating time, the nano-crystalline poly-crystal growth in the lateral two-dimensional simultaneously on the surface of the nano-crystalline poly-crystal with a three-dimensional direction of a new layer of poly-crystal growth surface; 45 steel in the quenched state , since the grain boundaries and having a relatively high defect density, so early in the deposition of nano-crystalline poly-crystal nucleation density is also large, resulting in two-dimensional directions poly crystal smaller scale, the performance of the beginning of the coating deposition is a dense, fine The scaly Organization. Ni-P alloy layer coating P content is closely related with the increase of the phosphorus content in the coating, coating organized by the nanocrystals into amorphous; TEM observation and analysis by X-ray crystal coating during the heat treatment behavior and crystallization product. Ni-10.6wt% P in the crystallization process the hexagonal metastable transition phase Ni ₅ the P ₂ exists, when the temperature reaches 400 ° C, crystallization completely, and its crystal process: Ni-10.6wt% P (amorphous) → Ni ₅ the P ₂ metastable phase Ni solid solution → Ni solid solution Ni _{3 P; P plating Ni-3.4 wt% Ni ₃ P precipitation during the heat treatment, and with the heat treatment temperature, nickel grain growing up. Electrodeposited Ni-P alloy coating corrosion resistance of the coating hardness and wear resistance of the findings show that: the coating corrosion resistance is closely related to the phosphorus content of the coating, in a variety of corrosive media, the phosphorus content showed different laws. After heat treatment, the corrosion resistance of the coating decreased significantly. Plated, phosphorus coating amorphous phosphorus coating has a higher hardness, the wear resistance is also significantly higher than the high-phosphorus coating. Coating after heat treatment, the hardness of the coating due to the precipitation of Ni ₃ P can be improved; phosphorus coating and high phosphorus coating after heat treatment, wear resistance, Yanshan University, Engineering PhD thesis is not very different. Of electrodeposited NiP alloy coating coefficient of friction and wear mechanisms related to the applied load, as the load increases, the wear form from minor wear and tear into oxidation wear, continue to increase the load, and finally the development of adhesive wear. In the bath for a certain amount of rare earth elements, rare earth elements on the electrodeposition NIP alloy plating solution and coating performance. The results show that: in the electrodeposited Ni-P alloy plating solution add a certain amount of rare earth compounds can improve the performance of the of NiP alloy plating solution and coating, rare earth dosage of Zg / L, the corrosion resistance of the coating. Adding a certain amount of rare earth in the bath, the coating containing the amount of P increases, the rare earth nor deposition of alloys, NIP No. The rare earth elements to improve the the electrodeposition NIP alloy plating solution and the coating performance is due to the adsorption characteristics of the rare earth ions in the electrode interface, increasing the cathodic polarization. Self-developed high-speed centrifugal electro-deposition device. Centrifugal electrodeposited Ni-P and Yang iP) of seven composite coating test the device, process parameters on the coating composition and coating performance. The results show that: the speed of electrodeposition NIP alloy; factors affecting the phosphorus content in the coating are mainly the pH value, current density can be increased by centrifugation electrodeposition method. Centrifugal electro-deposition (Ni Bu SiC composite coating in a much more content than conventional electrodeposition; composite coating particles evenly distributed; 8 content in the coating decreases with increasing temperature, with the current density, a concentration in the bath and cathode rotational speed increases; pH value content little effect on the coating; coating hardness, improved wear resistance, more content of the composite coating S I C, the better the hardness and wear resistance of the composite coating.}

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