Kenzo Miura

Friction and Wear Characteristics of Surface Modified SUS440C Spur Gears in High Vacuum.

In order to investigate the friction and wear characteristics of surface modified spur gears made of stainless steel SUS440C in high vacuum, gear tests were carried out under non-lubricating condition in vacuum to be on the order of 10-4 Pa. In addition, dynamic load on spur gear teeth with surface modified layer was evaluated. Electroless Ni-P alloy plating (Ni-P plating), sulfurizing and Sn plating with thermal diffusion (Sn plating) were employed. From the gear tests, the following results were obtained. (1) The friction coefficient of the surface modified gears was smaller than that of the non-coated gears. (2) The initial friction of Sn plated gear increased under low pressure and low rotational speed conditions. After Sn plated layer wore uniformly, the friction coefficient was the smallest by the lubricating effect of thermally diffused layer of Sn. (3) The sulfurized layer contributed to the reduction of initial friction. However, the friction behavior of sulfurized gear was the same as that of non-coated gears, after the sulfurized layer wore completely. (4) Wear amount and tooth profile error of Ni-P plated gears were the largest of all the test gears.

Scuffing Characteristics of Wear Resisting Steel and Steel with Surface Modification Treatment

Wear resisting steel (WRS), improved scuffing characteristics was newly developed in order to apply to the frictional parts for machinary. The two rollers tests were carried out using the newly developed WRS, steels with Ni-P electroless plating, and with electrolyzed and sulfurizing treatment. Then the scuffing characteristics of these materials were discussed.The anti-scuffing characteristics of WRS were very good and the frictional coefficient was as small as about (1/3) of SUJ2, a reference material. From the test results using WRS specimen of two kinds of hardness, the anti-scuffing characteristics of specimen of which the hardness was low was higher. The anti-scuffing characteristics of steel with Ni-P electroless plating were good. The part of Ni-P electroless plating layer remained during the test period but the other part of plating layer disappeared. On the other hand, the electrolyzed and sulfurizing layer which is effective for running-in, disappeared in a short time, and became that of base material.As the result of observation of surface and cross section of specimen, the white layer on the scuffing surface was found from 30 to 50μm thickness. It seemed that the layer is a martensite including supersaturatedly solidified carbon which is a part of cementite at the sub-surface dissolved by thermal and mechanical energies.

Development of Piston-Ring for Marine Diesel Engine. Actual Engine Test Result of Piston-Ring Made from Wear Resisting Steel.

In one direction of improving the material strength of a piston-ring of a marine diesel engine, a new wear resisting steel has been made efforts to develop in the expectation that it may supersede high phosphorus gray cast iron. For the newly developed wear resisting steel (later, wear resisting steel) we carried out wear tests and scuffing tests, and analyzed its test results in comparison with those of gray cast iron. After that we manufactured piston-rings using wear resisting steel. Piston rings made from wear resisting steel were installed the actual engine, and the actual engine test was carried out for 160.8 hours. We inspected the sliding surfaces of piston-rings after 29 hours and 160.8 hours. According to the test results, the wear amount of wear resisting steel was the same or smaller than that of gray cast iron, and the sliding surfaces of piston rings were normal and no severe wear such as scuffing was observed on them.

Influence of Hardness and Surface Modification Treatment on Scuffing of Wear Resisting Steel

A wear resisting steel was developed in the expectation that it may supersede high phosphorus gray cast iron for improving the strength of sliding elements of a marine diesel engine. In order to investigate the influence of the surface hardness and the surface modification treatment on the scuffing capacity of the wear resisting steel, the two cylinder test was carried out under oil lubrication. The test rollers had two kinds of hardnesses; one was 860 HV for bearings, and the other was 370 HV for sliding materials of cylinders. The electroless Ni-P alloy plating and sulfurizing treatments were employed. The scuffing capacity of the wear resisting steel was larger than that of the high chromium bearing steel SUJ 2. The scuffing capacity of the harder wear resisting steel was smaller than that of the softer one. The electroless Ni-P plating treatment slightly increased the scuffing capacity, while the sulfurizing treatment had no effect on the scuffing capacity of the wear resisting steel.

Vibration and Noise of Gears of Damping Alloy

This paper presents a study on vibration and noise of gears made of damping alloy. The logarithmic decrements of damping alloy were measured and compared with those of conventional steel. Vibration acceleration and sound pressure of helical gear pairs and spur planetary gears of damping alloy were measured under various running conditions using a power-absorbing-type gear testing machine, and the results were compared with those for conventional steel gears. Furthermore, the sound intensities of planetary gears made of damping alloy and conventional steel were also measured. The vibration and noise characteristics of these gears were determined. The vibration and noise of helical gear pairs and spur planetary gears made of damping alloy were found to be smaller than those of conventional steel gears.