Nickel-Molybdenum alloys were obtained from a plating bath containing molybdic acid, nickel sulfate, potassium sodium tartrate, sodium chloride, and ammonia water (for adjusting pH of the solution). Plating variables studied were metal % of Mo in the bath, total metal ion concentration, potassium sodium tartrate concentration, pH of the bath, cathodic current density, and temperature. The following results were obtained: (1) Mo % in the deposits increased with the increases in metal % of Mo in the bath and total metal ion concentration and the rise of temperature. (2) Potassium sodium tartrate concentration had no effects on the alloy composition. (3) Mo % in the deposits decreased with the increases in pH value of the bath and cathodic current density. (4) Cathodic current efficiencies for the alloy deposition decreased with the increase in Mo % in the deposits, which showed an evident upper limit.

抄録全体を表示

Electrodeposition of thin chromium layer on iron and steel sheets cathodically treated in dilute chromic acid solution was studied by electron microscopy. The results obtained were as follows: (1) At the early stage of electrodeposition, chromium epitaxially grew on the substrate, copying accurately the crystallographic orientation of base iron and steel sheets. (2) Even the thinnest film of such as about 15Å in thickness uniformly covered the substrate. (3) The rate and aspect of crystal growth seemed to depend on the crystallographic orientation of the chromium film. In the film of above 200Å in thickness, growth of pyramidal particles partitioned by four {011} planes was observed on the planes oriented within angle of 25° to the {011} planes. In the film of above 400A in thickness, the pyramidal particles changed to granular form, which deviated from the epitaxial growth. On the other hand, the planes oriented close to {111} or {011} planes showed uniform growth throughout each of the planes. The growth rate of {111} planes was found to be higher than that of {001} planes. (4) The dependence of chromium growth on crystallographic orientation could be interpreted in terms of epitaxial constraint of the substrate and the nucleation energy of electrodeposit.

抄録全体を表示

Effects of substrate conditions on electrodeposition of chromium layer and fine structure of that layer were studied by electron microscopy. The results obtained were as follows: (1) None of extremely thin oxide films on the substrate prevented the deposition of chromium. However, when a slightly thicker oxide film was present on the substrate, the orientation of chromium deposited on it did not always replicate that of the substrate. (2) Unless the surface roughness of the substrate was very remarkable, chromium completely covered the surface in uniform thickness. (3) Chromium film deposited on a mechanically polished surface was composed of aggregates of fine crystallites with random orientations, replicating accurately the worked surface layer of the substrate. However, in a thinner worked surface layer, such as of having been polished by buffing, the chromium deposit was found to be affected by the orientations of the underlying matrix. (4) Fine dotted diffraction contrasts were observed in chromium films. They would be due to dislocations, which had been either introduced in the course of electrodeposition (mechanism origin) or inherited from the substrate (structure origin).
Dislocations of the structure origin were confirmed by replication of cellular structure or martensite structure in chromium film which had been deposited on worked steel or low carbon martensite substrate.

抄録全体を表示

The mechanism for formation of Cr⁶⁺ compounds which were produced by high temperature oxidation reaction of Cr-Ca and Cr(OH)₃ systems was investigated. The following conclusions were drawn: (1) When Cr(OH)₃-Ca(OH)₂ system was burned, Cr⁶⁺ compounds were produced by two different mechanisms, which were distinguished by the boundary temperature of 300°C. At temperatures above 300°C, Cr⁶⁺ compounds were produced by the mechanism proposed by Nishino et al.; but at temperatures below 300°C, Cr⁶⁺ compounds were produced by the following reaction: 4Cr(OH)₃+4Ca(OH)₃+3O₂→4CaCrO₄+10H₂O (2) CrO₃ was prouced by burning of Cr(OH)₃ including oxidable anions such as SO₄²⁺; and the amount of CrO₃ compounds produced was maximum at 250°C. Therefore, it was impossible to prevent the production of Cr⁶⁺ compounds in the low temperature burning of real sludge. (3) When Cr-Ca system was burned, the amount of Cr⁶⁺ compounds produced became constant at a time at a temperature of 440-600°C; but, at temperatures above 700°C, the surface began to fuse and the reaction proceeded to the interior of particles so that the amount of Cr⁶⁺ compounds produced increased with the rise of temperature.

抄録全体を表示

The formation of Cr-Al diffusion coated layer was studied on 18Cr/10 Ni/Ti austenite stainless steel. The specimens of the steel were treated in HCl atmosphere by powder pack process with a diffusion coating agent composed of the mixture of Al and Cr powders. The results obtained were as follows: (1) The leading factors controlling the formation of Cr-Al diffusion coated layer, which were different from those controlling the formation of the layer of one element, were as follows: (a) Deposition rates of the two elements, (b) Deposition velocity of coating elements, (c) Mutual diffusion coefficient, (d) Time for diffusion coating. (2) Mean deposition rate of Al, deposition velocity of coating elements, and mutual diffusion coefficient increased; but mean deposition rate of Cr decreased with the increase of Al quantity in the diffusion coating agent. (3) Mean deposition rate of Cr, deposition velocity of coating elements, and mutual diffusion coefficient increased; but mean deposition rate of Al decreased with the rise of treating temperature. (4) Mean deposition rate of Cr increased; but deposition velocity of coating elements and mean deposition rate of Al decreased with the increase of treating time. (5) Mean deposition rate of Al was higher; but mean deposition rate of Cr and deposition velocity of coating elements were lower in argon atmosphere as compared with in hydrogen atmosphere. (6) The tendencies of mean deposition rates well corresponded with those of surface concentrations of specimens.

抄録全体を表示

Studies were made on the electrodepositions of copper from sulfate or cyanide baths and silver from cyanide bath under ultrasonic vibration. Discussions were made on the difference between presence and absence of ultrasonic vibration on the current-potential curves and the current efficiency-current density curves. It was observed that polarization was appreciably decreased owing to the reduction of diffusion polarization by the application of ultrasonic vibration. It was also observed that surface roughness and grain size of the deposited layer were improved by its application. These effects were particularly remarkable in silver deposition from cyanide baths, where the current density for operation was considerably increased under ultrasonic vibration for reducing the deposition time.

抄録全体を表示

Boriding of iron with B₄C was investigated for getting an extremely hard surface(Hv≅2, 000). Carbonates of alkali metals were used for accelerators for bonding. The results obtained were summarized as follows: (1) The most suitable composition of the bonding agent was 80wt% B₄C-20wt% Na₂CO₃. (2) The bonded layer was composed of Fe₂B, the hardness of which was 1, 400-1, 900kg/mm². (3) The bonding rate did not depend on the crystal grain size of iron. (4) The relation between the specific rate of bonding and the activation energy was derived, by which the value of activation energy was determined to be 25kcal/mol. (5) The mechanism of bonding of iron by treating with B₄C-Na₂CO₃ system was analyzed, and successive reactions including B₂O₃ and Na₂B₄O₇ were discussed.

抄録全体を表示