The deposition kinetics of alumina particle on a rotating substrate was examined by comparing the results obtained for two types of alumina dispersed nickel plating baths, the sulfamate and the Watts baths. For both baths, it was observed that the alumina content of the deposits and the size of the alumina particles in the deposits decrease with increasing rate of revolution of the cathode, when a rotating cylindrical cathode is used. In the successive processes of embedding particles into the composite, it was found that the process of detaining particles on the growing surface of the deposit is directly affected by the revolution rate of the cathode. According to the model previously proposed by the authors, the maximum size of particles caught by the cathode is inversely proportional to the revolution rate. In this investigation, this relationship was found for the deposits from the sulfamate solution.
The microstructure of the electrodeposited Ni-TiH2 composite coatings annealed at 1000°C in vacuum was studied by EPMA, X-ray diffraction analysis, optical and electron microscopic observation. The matrix of composite coatings was varied into Ni-Ti solid solution by heat treatment and Ti concentration in the solid solution increased with increasing the amount of TiH2 particles in the composite coatings. It was found that the fine particles formed by thermal decomposition of TiH2 particles in the electrodeposited composite coatings were various kinds of titanium oxides or titanium and nickel double oxides. These oxide particles formed colonies in the rang of 1-5μm in diameter. The colonies uniformly dispersed in the matrix. The density of colony increased with increasing Ti contents in the coatings. The grain growth of matrix was blocked by the surrounding colonies, so that the annealed composite coatings containing a large amount of Ti had a fine structure of matrix grains (1-3μm) and particles colonies.
Various kinds of non-metallic particles such as carbide, nitride, boride, and sulfide can be codeposited from electroless nickel plating bath. Most dispersoids were distributed uniformly in the Ni-P matrix. Taber Abrader test showed that silicon carbide has the highest wear resistance. Abrasion weight loss decreased with increasing amount of codeposits and reached a constant value above 2 percent by weight of SiC powder. The wear resistance of the heat treated SiC composite coatings was improved about three times than that of non-treated coatings. The SiC comosite coatings were more wear resistant than hard chromium. Boron nitride composite coatings showed lower friction coefficient than that of other conventional lubricating finishing materials. The electroless composite coatings would be very effective and usefull for many kinds of industrial functional parts from the standpoint of the excellent hardness and lubricity.
The alumina content of nickel-alumina composites electrodeposited on a rotating cylindrical cathode in an alumina dispersed Watts solution decreased With increasing revolution rate of the cathode. The maximum size of alumina particles deposited also decreased with increasing revolution rate. These new findings on the behaviours of the deposits have been studied in detail with measurements of the size distribution both of particles in the plating solution and of the particles in the composites. The increase in the revolution rate of the cathode displaced the cumulative size distribution curve of the particles embedded in the deposit to smaller size range. The particle size on the distribution urve, which corresponds to the efficiency of transfer of dispersed alumina is inversely proportional to the revolution rate. This observation can be explained in terms of an estimated value of the Hamaker constant of 2.5×10-19[J] for the heterocoagulation between alumina and nickel.
The electrodeposition of Cu-Ni alloys from pyrophosphate bath containing thioglycolic acid (TGA) was investigated. Total metal concentration and that of pyrophosphate in the bath was kept constant at 0.1M and 0.3M, respectively. The alloy deposition was carried out under various conditions; TGA and nickel concentrations in the bath, and current density. The Cu-Ni alloy from a pyrophosphate bath had a single phase and uniform solid solution with a copper-rich composition, and its appearance was dull and mottling. An addition of TGA to the Cu-Ni pyrophosphate bath resulted in an increase in the nickel content in the alloy deposits all over the range of current density examined. The increment of the nickel content in alloy deposits was found to be about 5-25%. The Cu-Ni alloy obtained from TGA-containing bath had an uniform, smooth and bright surface, and a bright alloy deposits like nickel in appearance was obtained from a bath of lower copper concentration. Electron-microscopic examination of the Cu-Ni alloy deposit revealed that the addition of TGA to the bath brought about a formation of fine grain structure. The effect of TGA on the electrodeposition of Cu-Ni alloy might be explained in terms of the complexation of TGA with copper and nickel ions in the pyrophosphate bath.
Electroplating of Cu-Sn alloys was studied by using the bath containing cupric sulfate, stannous sulfate, sulfuric acid, cresol sulfonic acid, Emulgen and benzalacetone. Copper deposited preferentially increased with increasing concentration of Cu2+ in the bath. The limiting current density for copper deposition increased with rising temperature and lustrous alloy layers were always obtained at potentials around -0.8V vs. S.C.E.
A study of electroless nickel-tin-phosphorus alloy plating from ammonia alkaline citrate bath (A-C bath) and from caustic alkaline citrate bath (C-C bath) containing sodium stannite has been made with reference to the effect of the tin content on deposition condition and the corrosion behavior of the alloy. It was found that the deposition rate increased with increasing amount of sodium stannite in A-C bath, but this effect was very small in C-C bath. The tin content in the deposits increased up to 19.2% in A-C bath and 12.4% in C-C bath. In a 0.5M sulfuric acid solution at 30°C, however, the tin cotent in the deposits from A-C bath increased about more than 7% and that from C-C bath increased more than 12%. Severe corrosion of the alloy in the solution is due to the formation of metastable phase Ni3Sn4. The corrosion resistance of the depeposits, containing 2.8% tin and 4.4% phosphorus, from A-C bath, and of the deposits containing 8.4% tin and 8.3% phosphorus, from C-C bath was excellent.
The purpose of this investigation is to form a graphite-dispersed Fe-Si films on steel by reaction with fused salts containing NaCl, KCl, NaF, Na2SiF6, and Si. Optimum operating condition found is as follows; [Composition of fused salts] NaCl:KCl=1:1 (weight ratio), NaF: 22mol%, Na2SiF6: 4.9mol%, Na2SiF6:Si=1:4.5 (mol ratio), [Reaction temperature] 900°C, [Reaction time] 3hrs. For the film formed on a 0.8% C steel specimen, it was found that the thickness is about 180μm, the Vickers hardness number (Hv) is 700, the amount of deposit is about 35mg/cm2, and the friction factor against steel ball is 0.1-0.2.
Ni-Co alloy deposits were obtained by electroless plating from an acetate bath using dimethyl-amine borane at a rate of about 7μm/h at 60°C. Thallous nitrate was employed as a stabilizer of the bath. Under these conditions, both thallium and boron were co-deposited into Ni-Co alloys. It was, however, confirmed that boron content in the alloy deposit decreased significantly with an increase of thallous nitrate in the bath. Internal stress, electrical resistance and hardness of the alloy deposits were discussed on the basis of the composition of Ni-Co alloys. The internal stress of the Ni-Co alloy deposits seemed to decrease with a decrease in boron content of the alloys. The specific resistance of the Ni-Co alloy deposits as-plated was found to be 60-80μΩcm. However, it decreased to about 20μΩcm upon heat treatment at 400-600°C in vacuum. The hardness of the alloy deposits heat-treated at 400°C depended on boron content in the alloys; the higher boron content gave rise to the higher hardness of the alloy deposits up to that of hard chromium coatings.