Masaki Kohno

Seizure Resistance of Thermally Diffused Layer after Sn-Plating in Two-Roller Test. Case of Grease with Molybdenum Disulfide Additive.

To clarify the seizure resistance of stainless steel rollers of which the surface layer was thermally diffused after being Sn-plated, a two-roller test was carried out with grease lubrication. From the tests, the following results were obtained. The coefficient of friction of the roller with the Sn-diffused layer at the incipient stage of seizure, when lubricated with grease containing molybdenum disulfide additive, was considerably higher than that without a diffused layer. The load at the incipient stage of seizure of the roller with the diffused layer was larger than that of the roller without the diffused layer, and the effect of the diffused layer on the increase in the seizure resistance of the roller was recognized. However, the seizure resistance of the roller was decreased due to the molybdenum disulfide additive. The critical temperature of the roller with the diffused layer was higher than 400°C, and this was higher than that without a diffused layer.

Frictional Characteristics of Thermally Diffused Layer after Sn-Plating in Two-Roller Test.

To clarify the seizure resistance and the frictional characteristics of a stainless steel ball, which was thermally diffused after being Sn-plated, the four-ball test was run under dip-feed lubrication and thin film lubrication. From the seizure test, the following results were obtained. Under dip-feed lubrication, the coefficient of friction was decreased with increasing thickness of the Sn-diffused layer, and the seizure resistance of the ball was increased with increasing thickness of the diffused layer. The seizure resistance of the ball in which the diffused layer was 8 μm thick was about 2.6 times larger than that without a diffused layer. Furthermore, under thin film lubrication, the running time at the incipient stage of seizuring with balls in which the thickness of the Sn-diffused layer exceeded 4 μm was about 5 min, independent of the thickness of its layer, and this was considerably longer than that without a diffused layer.

Effect of Lubricants on Scoring Resistance of Gears Sulphurized at Low Temperature. Test Results in Four-Ball Test and Gear Test.

This paper presents a study on the effect of lubricants on the seizure resistance of balls and the scoring resistance of gears, which are sulphurized at a temperature of about 463 K. The seizure resistance of the balls was investigated by a four-ball machine, and the scoring resistance of the gears, by a power-circulating gear machine. As a result, it was clarified that the seizure resistance of the sulphurized balls and the scoring resistance of the sulphurized gears were about 1.5-2.0 times larger than those of the unslphurized ones, and a considerable relationship between the seizure resistance in the ball tests, and the scoring resistance in the gear tests was recognized. Further, the scoring resistance of the gears was increased with increasing viscosity of the lubricants.