Water-accelerated chemical reaction for producing gear teeth with high form accuracy and fine surface finish

A new method was investigated for high-accuracy fine finishing of gear teeth surfaces using a water-lubricated tribo-chemical technique. A pair of shaved gears with rather low surface roughness was rotated in water “lubricant” for 30 minutes so that the gear tooth surface contacting the mating tooth was “worn” to a mirror-surface and ideal tooth profile, due to the tribo-assisted mechano-chemical mild erosion of only the contacted area. The wear rate was 2.0 micrometer per 20000 meshings, corresponding to a wear of one atomic-radius-thickness per meshing. Oxidation of the steel surface by water molecules is proposed as the dominant wear process. Operation noise from the gear pair rotation was drastically reduced to lower than about 10–15 dB compared to conventionally machined gear surfaces(30 dB in average), as a result of the wear of the tooth surface to form a best-fit profile. The noise increased with further processing of the gear pair. Thus, there is an appropriate number of rotations for a suitable surface wear treatment. This new and simple procedure for surface treatment assures energy savings, and does not require expensive honing techniques or high-accuracy grinding tools. The wear mechanisms used in this process are discussed along with the application of the technique to other processes for precision finishing.