Effect of Fine Particle Bombarding Process on Tooth Surface Properties and Tooth Surface Strength of Carburized Gears (1st Report, Effect on Tooth Surface Properties)

Abstract

Fine particle bombarding (denoted as FPB) is one of the surface modification processes that makes fine (20-200μm in diameter) and hard (Hv 750-1000) particles impact with the metal surface at a high speed (more than 100 m/s), which is similar to shot peening. Although FPB has been already applied to extend lifetimes of a die and a metal cutting tool, and to reduce friction on the contact surface, the influence on the tooth surface strength of gears has not been clarified. The purpose of this study is to determine quantitatively the effect of FPB on the tooth surface strength of carburized gears and to clarify the factors caused by FPB that influence on the tooth surface strength. First, the author examined the tooth surface properties such as residual stress, roughness, hardness, surface texture, etc. using test gears processed by the FPB under three different conditions of arc height. A test gear performed by conventional impeller-type shot-peening was also used for comparison with the FPB. Next, durability tests were carried out using the gears to measure the tooth surface strength. The results showed that the FPB is effective to increase the tooth surface strength compared to conventional shot-peening. In the 1st report, the effect of the FPB on the tooth surface properties is described.