EFFECT OF SHOT PEENING TREATMENT ON ROLLING CONTACT FATIGUE PROPERTIES OF USTEMPERED DUCTILE IRON

摘要

Austempered ductile iron (ADI) has lower density and higher damping capacity in comparison with steel. To evaluate the applicability of ADI to electric car driving gears, rolling contact fatigue (RCF) tests were carried out using two rollers of shot peened ADI for lower rotating velocity roller and case hardened alloy steel for higher one in gear oil lubricant. In case of line contact condition, RCF lives of ADI tend to increase by shot peening in the higher stress region, while slightly reversed in the lower stress region. On the other hand, in point contact condition, RCF lives is not affected by finishing of the surface. These results suggest that surface compressive residual stresses and hardening introduced by shot peening counterbalance the harmful effects due to surface roughening.