High compressive residual stress in steel gears leads to improved

fatigue life, especially at the roots of the gear teeth. The production

of large compressive residual stress profiles in steel gears is one of

the most desired results of carburization. The goal of this study was to

compare the residual stress profiles generated by two different

carburizing processes. Low-pressure carburization (LPC) with 20-bar

nitrogen quench and traditional atmospheric carburization (AC) with oil

quench are being studied to compare the residual stress profiles of each

process. This study was designed to compare the two carburization

processes using matching carbon profiles. Three different carbon

profiles with pre-selected effective case depths and surface carbon

contents were compared with results from both the LPC and AC processes.

This project has been designed to simulate the production and

carburization of 8620H steel gears. 8620H steel was chosen as

representative of gear material. The project is divided into three

steps; the first step of which was to create target values of suitable

carbon profiles via atmospheric carburization in 8620H steel. In order

to produce differing carbon profiles, the atmospheric carbon potential

will be varied during processing. Secondly, cycle parameters will be

developed for the LPC process that will match the carbon profiles

produced by atmospheric carburization. Thirdly, the steel coupons

carburized by both LPC and AC will have their residual stress profiles