Wear of Case-Hardened Spur Gears. Effect of Oil Viscosity, Additives and Temperature.

Abstract

The wear of case-hardened spur gears running under a constant high load was studied. The lubricating oil viscosity, kinds of additives and their amounts, and lubricating oil temperatures were changed. In order to study the effect of oil temperature on the wear of the tooth surface, the temperature of the oil was changed from 60°C to 90°C for the same sample. Moreover, the temperatures of three kinds of oils which have very different viscosities at room temperature, were varied between 60°C and 105°C while the oil viscosity was unchanged. It was shown from the test results that tooth surface wear is not greatly affected by the amount of ZDTP antiwear agent, but EP additives are less effective against wear than ZDTP additives. The viscosity of lubricating oil and its temperature greatly affect the wear of the tooth surface. Combining all the wear data with those of the tooth surface strength, it was observed that the higher the load, the wider the scattering of wear, and also in the case of the same running load, the lower the wear, the longer the life of the tooth surface strength.