A high-power YAG laser was applied to the surface hardening of carbon steels containing 0.18∼0.54wt%C, and the relationships between laser processing conditions and surface hardening were investigated by hardness and microstructure.
The structure of the hardened zone underwent complete martensitic transformation in all of the carbon steels tested, and its hardness increased with greater carbon content. Under identical irradiation conditions, the hardened zone expanded with increasing carbon content. A hardened zone extending from the surface to a depth of 1.0mm was obtained at a laser power of 1.0kW and a scanning speed of 1mm/s.
It was found that in the surface hardening of carbon steels, a high-power YAG laser can be used to control the hardened zone by selecting the appropriate irradiation conditions.

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Electrochemical measurements and metallurgical observations have been made to clarify the relationship between NaOH solution temperature and the dissolution behavior of Al-Fe alloy. Etching weight loss was measured for Al-Fe alloy specimens dipped into 3%NaOH+1%NaAlO₂ solutions at four temperatures (298, 313, 333 and 353K). As solution temperature rose, etching weight loss increased exponentially. It was found that etching weight loss was more strongly affected by solution temperature than by NaOH concentration.

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Titanium nitrides were prepared by high-temperature nitriding and reactive ion plating, and their semiconducting properties were studied by photoelectric polarization. All the nitrides prepared by nitriding showed negative photopotential, which means that they exhibited n-type conduction. The magnitude of the photopotential, however, varied depending on the nitriding temperature, form -10^-5∼-10^-4V at 773∼873K to about -10^-7V at 973∼1473K, and the properties of TiN (N=47.12at%) prepared by reactive ion plating were similar to those of the latter. Subsequently, the dissolution reaction of titanium nitride in sulfuric acid solution was inferred from the semiconducting properties and valency, which could be calculated from the quantity of electricity and the amount of titanium dissolved during potentiostatic polarization. The lower nitride Ti₂ N dissolved according to the process Ti₂N+4H⁺=2Ti³⁺+NH₄⁺+3e^-, whereas with the higher nitride TiN the reaction was assumed to involve Ti⁺. Light irradiation of the surfaces of the both nitrides generated a reaction involving positive holes.

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Numerical analysis of the electric current distribution during tin plating in plating cell measuring 15mm in width and ca. 1, 000mm in length, in which the plating solution was supplied through the solution inlet on the center of an unconsumable anode, was carried out, and compared with experimental results. It was found that;
(1) Current density in the cell can be found using the Laplace equation.
(2) The shape of the solution inlet had a great influence on the uniformity of tin coating thickness. Using inlets of identical area, making inlet width less than cell width, so that part of the electrode remains between the inlet and the cell walls on either side, was advantageous in maintaining uniform coating thickness distribution. The vertical (internal) electrode on the side wall of the inlet also contributed to the same aim.
(3) The electrode current density near the inlet was about twice that of the usual sites, compensating for the adverse effect due to the absence of an electrode.

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The inhibiting effect of various organic reagents on the dissolution of aluminum in 1, 1, 1-trichloroethane (CCl₃CH₃) have been analyzed statistically using data previously obtained on the basis of variance from a) the kind of functional groups, b) the number of functional groups and c) the carbon skeleton structure (aliphatic or aromatic). The results are summarized as follows; 1) The kind of functional group resulted in a recognizable difference in inhibiting effect, which, in the case of monofunctional groups, increased in the order: ethers (A₁)<phenols (A₂) <alcohols (A₃)<esters(A₄)<nitrocompounds(A₅)<amines(A₆)<ketones(A₇)<nitriles(A₈). Imides (A₉) had no inhibiting effect, since they are insoluble in CCl₃CH₃, 2) There was a clearly recognizable difference between monofunctional and difunctional groups. The quantity of organic reagents added to the CCl₃CH₃ to inhibit the dissolution of aluminum differed depending on the kind of functional groups, and difunctional groups were lower in concentration than monofunctional groups, at 5 to 45%, 3) There was no recognizable difference in inhibiting effect between aliphatic and aromatic compounds. Standards for the selection of inhibitors are provided by the above analysis.

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Electroless films of Co-N (boron-free) alloy and three Co-B alloys having boron weight percentages of 1, 3 and 6wt% were prepared, and the effect of film composition and crystal structure on their magnetic properties was studied. It was found that in the Co-N alloy, film structure and magnetic properties were independent of heat treatment, while in the Co-B alloy films, an increase in boron weigt percentage increased the crystallization temperature under heat, treatment (1wt%: 200°C, 3wt%: 300°C, and 6wt%: 400°C) but decreased the coercive force, residual magnetic flux density and saturation magnetic flux. Maximum permeability also decreased with crystallization by heat treatment. It was also verified that the deposition of Co₂ B under heat treatment affects the fine structure of the film and produces a significant increase in coercive force and residual magnetic flux density.

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The effects of complexing agents and additives on non-cyanide electroplating is studied. It was found from polarization curves that very strong adsorption of additives occurred at electrodes and that cathode potential decreased and polarization increased during electroplating. According to observations by electron microscopy and X-ray diffraction, the electroplated layer became microcrystalline instructure and had a very strong orientation in the (220) plane.

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Titanium films were electrodeposited on 304 stainless steel by constant current and pulse current methods from the eutectic mixture of KCl-NaCl-LiCl containing 2mol% K₂TiF₆, with and without the additive CeF₃. The influence of electrodeposition conditions on the crystal orientation and morphology of the films was investigated by X-ray diffraction and scanning electron microscopy, respectively. In the case of melts without CeF₃, increasing temperature caused the Ti films electrodeposited by a constant current to exbibit (002) preferred orientation, while those deposited by pulse current exhibited (110) preferred orientation. In the case of melts with 1mol% CeF₃, increasing temperature caused the preferred orientation of the Ti films to change to (110) independent of current waveform. The morphology of the Ti films showed well-crystallized grains, which became large with increasing temperature. Under identical conditions, grains of the films from the melts with CeF₃ were larger than those from those without.
Corrosion resistances were estimated by anodic polarization in 3% NaCl solution at 298K. It was found that the films deposited by pulse current or from melts with 1mol% CeF₃ had better corrosion resistance than those obiained at constant current or from melts without CeF₃.

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With the objective of improving the oxidation resistance of TiAl intermetallic compounds, Ni-Al composite coatings were formed by combination of wet (electroplating of Ni) and dry (pack cementation of Al) processes. The coatings consisted of Ni-Al and Ni-Al-Ti layers. The oxidation resistance of the coated specimens were evaluated by a cyclic oxidation test at 1373K. The Ni-Al composite coatings effected a significant improvement in the oxidation resistance of the TiAl alloy, but not so much as for specimens that were aluminized only. The Ni and Al in the Ni-Al composite coating layer gradually diffused into the substrate during the oxidation test, and this determined the effective life of the coatings.

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