PROPERTIES OF ELECTRODEPOSITED AMORPHOUS Ni-W-P-SiC COMPOSITE COATINGS

The Effects of heat treatment temperature on the hardness,wear resistance and structure of the amorphous Ni-W-P-SiC composite coatings have been investigated.The results show that Ni-W-P-SiC composite coatings are amorphous under 300℃, partially crystalline at 300-400℃,and crystalline when heat treatment temperature reaches 400℃,the crystals being fine Ni3P phase particles.The hardness,wear resistance and the crystallization temperature of the composite coatings increase when an additive is added into the bath.The hardness and wear resistance of the coatings increase with increasing heat treatment temperature,and they will reach their peak values when the heat treatment temperature reaches 400℃.Corrosion experiment indicates that the corrosion resistance of amorphous Ni-W-P-SiC composite coatings in various kinds of corrosive media except nitric acid is better than that of stainless steel 1Cr18Ni9Ti.Scanning electron microscopy observation shows that the additive has no effect on the surface appearance of the coatings,but the current density and the pH value have considerable effects on the surface appearance.

Electrodeposition of Ni-W Amorphous Alloy and Ni-W-SiC Composite Deposits

Ni-W alloys and their composite deposits are electroplated on the metals when an appropriate complex agent is selected on the base of the theories of electrochemistry and complex chemistry, and the principle of induced codeposition. Effects of the bath composition, pH value, temperature and current density on the electrode position of Ni-W alloys and their composite deposits have been investigated, and the effect of heat treatment temperature on the hardness, structure and cohesive force of the amorphous Ni-W alloys and their composite deposits are also discussed. Results showed that the alloys containing more than 44 wt pct W content and the composite deposits containing 7.8 wt pct SiC content could be obtained by making use of the appropriate bath composition and plating conditions. Alloys and their composite deposits with over 44 wt pct W content show amorphous structure. The hardness of amorphous Ni-W alloys and their composite deposits increases obviously when heated, and can reach to 1350 HV and 1520 HV respectively for 46 wt pct W content. The cohesion on Cu, carbon steel and stainless steel is very good.

Effect of Attapulgite Added in Plating Bath on the Properties of Ni/TiC Nano-composite Coatings

Pure copper plates were coated by Ni-TiC dipulse current plating method. The effects of adding different concentration（ranging from 0.5 g/L to 3.0 g/L） of attapulgite nano particles to the plating bath on the surface morphology, wear resistance, and oxidation resistance of Ni/TiC/Attapulgite nano-composite coatings were investigated. The experimental results show that the composite coating is flat and compact with adding 3.0 g/L in the bath, and the coating preferred orientation is changed from the planes（111） to（200）. The coefficient of the composite coatings decreases from 0.68 to 0.18 with increasing content of attapulgite in the bath, a mixed mode of adhesive-abrasive wear occurs for all coatings, and the wear mechanism shows a transition from adhesive-abrasive to predominantly abrasive wear mechanism when the concentration of attapulgite is beyond 1.5 g/L in electrolyte. The oxidation resistance of composite coatings is the best prepared when adding attapulgite particles at 0.5 g/L in the bath, the oxide mainly consists of a NiO phase by X-ray analysis.

Corrosion behavior of Zn-Ni-Al_2O_3 composite coating

The corrosion behavior and anti-corrosion mechanism of the Zn-Ni-Al2O3 composite coating were investigated by SEM, EDS and XPS. The results indicate that the corrosion type of the Zn-Ni-Al2O3 coatings in neutral 5 wt.% NaCl solution is uniform corrosion. The presence of compact and uniformly dispersed nano alumina particles substantially inhibits the corrosion of Zn-Ni-Al2O3 composite coatings. In the initial corrosion stage, the corrosive products of Zn-Ni matrix form a compact ZnCl2·4Zn(OH)2 layer. With the development of corrosion, some nano alumina particles are embedded and form a Ni enrichment layer. In Ni enrichment layer, Ni presents as Ni and NiO.

Oxidation Behavior of Fe26Cr1Mo Stainless Steel in the Presence of Ni-La_2O_3 Electrodeposited Composite Film

The oxidation behaviors of Fe26Cr1Mo with and without the Ni La 2O 3 electrodeposited composite film have been investigated by thermogravimetric analysis (TGA) and a scanning electron microscope equipped with an energy dispersive analytical X ray system(SEM/EDAX). The experimental results show that the oxide scale growing on Fe26Cr1Mo exposed at 900 ℃ spalled severely during cooling, while after the stainless steel was coated with the Ni La 2O 3 electrodeposited composite film, its high temperature cyclic oxidation resistance was significantly improved. The reason is that a La 2O 3 modified NiO scale, which has a superior adhesion to the substrate, was formed on the Fe26Cr1Mo stainless steel coated with Ni La 2O 3 composite film.

Effects of the Composition of Electrodeposited Fe-Ni-P Alloy on the Thermostability and Magnetic Properties

The magnetic properties, structure defects of electrodeposited Fe-Ni-P alloys with various compositions and the thermostability at amorphous state have been studied by DSC, positron annihilation and electronic integrating instrument methods. The results show that the thermostability of amorphous Fe-Ni-P alloys increases with Fe content. Emergence and recrystallization of stable phases defer as the P content of the coating increases. The minimum H-c, B-r and P-h occur at 9.4 P (wt pet) content. Maximum H-c, B-r and P-h occur at the weight ratio of Fe to Ni equaling to 1/9.

Effect of Particle Conductivity on Fe-Si Composite Electrodeposition

Coatings containing Fe-Si or Si particles were electrodeposited on 3.0%（mass fraction） Si steel sheets. The surface morphology, the cross-section and the silicon content of coating have been investigated, respectively. It was found that the number of particles on the coating surface and cross-section significantly decreased with increasing silicon content in the applied particles, leading to a decrease of the silicon content of coatings. About 10.2% silicon content of coatings deposited with Fe-30%Si particles can be obtained, whereas that for Si particles was only 2.9% at a particle concentration of 100 g/L and current density of 2 A/dm2. This is mainly attributed to the conductivity of applied particles. High conductivity can promote the co-deposition of the particles. With increasing silicon content in the particles, their conductivity decreased sharply, resulting in the decrease of silicon content of coatings. Present work may initiate a new method to modify the particle content of the composite coatings via changing the conductivity of the particles during the composite electrodeposition. In this paper, a possible mechanism was proposed to explain the phenomena.

6.5 wt%Si high silicon steel sheets prepared by composite electrodeposition in magnetic field

A new preparation method of near-net-shape 6.5 wt% Si high silicon steel sheets was proposed by combining composite electrodeposition(CED) and diffusion annealing under magnetic field. The obtained sheets were characterized by scanning electron microscopy, energy dispersive spectrometry, analytical balance and a silicon steel material measurement system. The results show that the surface morphology,the elemental distribution, the cathode current efficiency and the silicon content of coatings were obviously influenced by the micro and macro magnetohydrodynamics(MHD) flows under magnetic field.With the effect of magnetic field, the silicon particles content of coatings showed an increasing trend and the diffusion process showed that an approximately uniform 6.5 wt% silicon steel sheet has been successfully obtained. The magnetism measurement showed that the high silicon steel sheet has the lower iron loss, and the iron loss further decreased under magnetic field. The new method proposed in this article,which is more environmentally friendly and low energy consumption, is feasible to prepare high silicon steel sheets.

Effect of activators on the properties of nickel coated diamond composite powders

Nickel coated diamond composite powders were fabricated via a newly developed direct electrodeposition technique. The effects of activators on the coating of diamond were firstly investigated and diamond grinding wheels were then prepared from Ni-coated diamond composite powders with different activators. The microstructural characterizations of this composite powders were finally conducted by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, and the mechanical and tribological properties of as-prepared diamond grinding wheels were also measured. There are changes in microstructures and properties of the composite powders with activators. The activator concentration also has an influence on the morphologies and phase structures of the Ni coating on diamond particles.The composite powders with more compact coating of nickel can be prepared by adding 1 g dm^（-3） or more AgNO_3 as an activator to electrodeposit nickel on diamond. The mechanical and tribological properties of diamond grinding wheels were significantly improved when the coating phase structure of Ni crystal grew with（111） plane orientation on the surface of diamond particles. The wheels made from nickel coated diamond composite powders possessed the advantages of easy preparation and outstanding tribological properties. Therefore, Ni coated diamond composite powders exhibit a great potential to be extensively applied in diamond cutting and grinding tools.