TiC coatings were deposited from mixed gases of TiCl4, CH4, H2 and Ar onto steel by the DC glow discharge method at a total pressure of 4 Torr and temperatures of 430-700°C. Micro Vickers' hardness measurement and X-ray microanalysis revealed a correlation between hardness and coating composition. X-ray photoelectron spectroscopy was carried out to investigate the binding state of the elements in the coatings. The results obtained are as follows: 1) The hardness of the coatings varied with the coating conditions, and coatings with Vickers' hardness of 2300-3000 were obtained at a TiCl4 flow rate of 3-8mL/min and substrate temperatures of 475-700°C. 2) The hardness of the coatings was determined by chlorine content and excess carbon content, and coatings with Vickers' hardness of 2300-3000 contained 5at.% chlorine and 45-60at.% carbon. 3) In coatings with more than 5at.% chlorine, in which there was a compensative relation between the carbon and chlorine content, both the titanium content and the sum of carbon and chlorine content were constant at 50at.%. 4) Incorporation of graphite-like carbon reduced the hardness of the coatings containing excess carbon.
Vapor-deposited MgNc films, prepared by two different processes were investigated for changes in the electric properties resulting from the thermal rearrangement of the molecules. The results obtained were: (1) Resistivities of as-deposited MgNc-a and-b films were 1.23×103 and 5.06×102 ohm·cm, respectively, and these values changed with thermal treatment to 6.76×101 and 3.48×102 ohm·cm, respectively. (2) The activati on energy of carrier formation was almost the same (about 0.30-0.35eV) for all the MgNc films investigated, indicating that all had the same impurity level. (3) The impurity level was induced by adsorbed oxygen, and the formation of O-2 radical was accompanied the formation of hole carriers. Using ESR measurement, the car rier density was calculated to be about 1018cm-3 for MgNc-a films. (4) Mobility increased some 24-fold with crystallization.
The adsorption of Cu2+ ions on MnO2 was examined as a function of pH and concentrations of Cu2+ and MnO2. The adsorption isotherm shows that the surface concentration of adsorbed Cu2+ increases with pH and concentration of Cu2+ in solution, and that, at higher coverages, the surface concentration is lower than predicted by the Langmuir isotherm The behavior was characterized by considering the stoichiometry and equilibrium and concentration conditions of the adsorption. The surface acid hydroxyl groups, ≡MnOH(a), react with Cu2+ ions to form the following two surface complexes.≡MnOH(a)+Cu2++NO-3_??_≡MnOCu+·NO-3+H+, 2≡MnOH(a)+Cu2+_??_(≡MnO)2Cu+2H+. The equilibrium conditlons of these surface complexations are given by. K1int=Q1eq exp (B1[≡MnOCu+·NO-3]), β2int=Q2eq exp(B2[(≡MnO)2Cu]), where K1int and β2int are“intrinsic”stability constants of[1:1]and[1:2] surface complexes, Q1eq and Q2eq are concentration quotients at equilibrium, and B1 and B2 are constants expressing the extent of suppression of surface complexation by the respective complexes. The equations of equilibrium conditions and of concentration conditions for both solution and surface species were fitted to the adsorption isotherm, and the values of the constants were determined by the nonlinear leastsquares method. The values are: K1int=8.15×10-3m3mol-1, β2int=2.41×103m-1, B1=3.81×106m2mol-1, and B2=1.62×106m2mol-1 at an ionic strength of 0.1 (NaNO3) and 25°C. These values well describe the observed adsorption behavior.
Composite plating can be of a variety of types according both to the metal base and to the dispersed particles added, which may have a great effect on its properties. Only a few studies, however, have been reported on the plating properties. This paper describes the effect of various kinds of dispersed particles, their grain size and concentration on the wear properties of the composite Ni-5 %P plating, making use of the fact that there is difference in hardness between the matrix and the particles dispersed. The following conclusions were obtained. 1. Particles dispersed in composite Ni-P plating affected its wear properties, and dispersion of Si3N4 particles was more advantageous in terms of the wear properties of the plating than any other particles used. 2. Smaller particles were preferable from the standpoint of higher wear resistance of the plating. The smallest grain size used for dispersed particles in this study was 0.7μm. 3. Si3N4 particles included in the plating affected its wear properties and coating strength. The most desirable inclusion was in the range of 5 to 15 area%.
The corrosion behavior of inhomogeneous Zn-Ni alloy films electroplated on iron substrates specimens has been studied. Zn-Ni alloy was electroplated in a Hull cell, and immersion tests were carried out in 3% NaCl solutions and in pH6 buffer solutions. In both solutions corrosion took place heterogenously and caused grooves. In the 3% NaCl solutions, both red rust and white rust were formed, the red rust appearing only in a thick layer region, while in the buffer solutions, rust formation was not observed. Corrosion potential and pH at various positions on the specimen were measured. In the 3% NaCl solutions, pH changed markedly depending on position, while in the buffer solutions, the corrosion potential changed. This indicates that a macroscopic corrosion cell is formed along the specimen, and that the buffer capacity of the solutions affects the corrosion behavior.
Fe-Al alloy layers are formed on the surface of iron specimens, being simultaneously dissolved in liquid aluminum in the reaction between iron and liquid aluminum. Effects of the iron in liquid aluminum on the thickness of alloy layer have hardly been investigated in connection with the weight loss of iron specimen. In this study, behaviors of the iron in liquid aluminum were investigated by several methods. The following results were obtained. When an iron specimen is immersed in the upper portion of an aluminum bath, the iron content is uniform in the bath. In the case of immersing the iron specimen in the lower portion, however, the iron content is higher in the lower portion than in the upper portion of the bath. Thickness of the alloy layers rapidly increases above a certain value of the iron content in the bath. This critical value changes by the immersion time and compositions of the bath. On the other hand, the weight loss of the iron specimen decreases with increasing iron content. The reason why the alloy layers thicken with increasing iron content in liquid aluminum is that the iron content near the iron specimen in the bath with higher iron content increases faster than in the bath with lower iron content, and that the dissolution speed of the alloy layer into the bath, therefore, decreases remarkably.
Bi-metallic joints with iron and aluminum produced by casting aluminum from above the steel inserts in the molds after the iron has been subjected to immersion in molten aluminum or aluminum alloys to produce a bonding layer, have high heat conductivity and high bonding strength compered with those of chilled castings. Bonding strength of the joints by this process, called Al-Fin, has not been investigated in detail. In this study, therefore, the effects of the thicknesses of Fe2Al5 and FeAl3 alloy layers, and the alloying elements in the molten aluminum and solid iron on the bonding strength were investigated by tensile strength and shear strength tests. The following results were obtained. Bi-metallic joints were almost always fractured in a Fe2Al5 phase by the tensile test, and the bonding strength increased with decreasing thickness of Fe2Al5. Addition of Cr and Ni into iron remarkably decreased the thickness of the alloy layers, and Fe-18% Cr-8% Ni steel indicates the bonding strength highter than 12kg/mm2.