LOAD-CARRYING CAPACITY OF AUSTEMPERED DUCTILE IRON (ADI) GEARS - INFLUENCE OF SHOTPEENING ON SURFACE DURABILITY OF ADI

摘要

In this paper, an application of austempered ductile iron (ADI) to gear material is investigated concerning the load-carrying capacity, in particular, the surface durability, using a power-circulating type gear testing machine. It is practical that a hardened steel such as case-carburized one is used for pinions to increase its bending strength and ADI is used for large gears to use its advantages such as near-net-shape casting. The surface durability of cermet-hobbed ADI gears approaches to that of hardened steels if an adequate tooth profile modification is made. In this case, it is necessary that shot-peening is utilized to the tooth of ADI gears to increase its bending strength. The surface durability of shot-peened ADI gears is lower than that of cermet-hobbed ADI ones. In order to clarify the reason of it, the surface integrity, for example, surface roughness, hardness, residual stress and retained austenite is investigated. Especially, the influence of surface roughness on surface durability of ADI is investigated using a disk machine with rolling and sliding.