The wear test between two tungsten-cobalt layers electrodeposited on mild steel rings was carried out, using an Amsler's wear testing machine, the load being 50kg, and the revolution slip without lubrication 10%.
Compared with the result of the hard chromium electrodeposit or water-quenched high carbon steel test under the same condition, the wear-resistivity of the tungsten-cobalt deposit was far superior.
The surface of quenched steel was soon in the beginning covered by thick oxide film and worn out markedly, and the hard chromium deposit layer was also worn rapidly and broken down within 10, 000 revolutions. In contrast with those, the wear loss of the tungsten-cobalt deposit was very small even after 100, 000 revolutions.
Such high wear-resistivity of the tungsten-cobalt deposit could be attributed to its characteristic property that the hardness does not decrease at a high temperature, while the hardness of the other two falls when the temperature rises over 300°C by friction heat, resulting in the breakdown of the layer.
The wear between the tungsten-cobalt deposit and chromium deposit or quenched steel was also studied.

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Plating speeds and utilization efficiencies of sodium hypophosphite of various caustic alkaline electroless nickel plating solutions were measured. Compared to the acid electroless nickel plating solution, the caustic alkaline electroless plating solution had not any merit.
The optimum composition of the caustic alkaline plating solution was Ni-salt 0.1M/l+Na-citrate 0.2M/l+NaH₂PO₂ 0.1M/l+Borax 0.1M/l, the pH of the solution being 8.0-8.5.

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In order to study wear problems of porous chromium plating vs. cast iron, the radiotracer technique was applied. The flat surface to be tested was porous-chromium-plated and activated in an atomic pile. This surface was rubbed reciprocatingly under dry condition with a non-active and highly wear-resistive cast iron specimen of flat surface. The wear amount was determined by measuring the radiation intensity of wear debris produced and of chromium transfered to the cast iron.
As a result, it was found that the wear amount changes depending on the testing time and load as follows:
1) There is a certain critical time when the time-rate of wear changes for any testing load except the least load.
2) Before the critical time, the time-rate of wear is independent of the load.
3) After the critical time, the time-rate of wear is proportional to the load.

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