Mechanical properties and rolling-sliding wear performance of dual phase austempered ductile iron as potential metro wheel material

Abstract

Dual phase austempered ductile iron (dual phase ADI) was produced through intercritical austempering with various partially austenitizing temperatures. Partial austenitization within the intercritical interval has a profound influence on the amount and morphology of microstructure in dual phase ADI. The influence of partially austenitizing temperatures on the mechanical properties and rolling-sliding wear performance of dual phase ADI were also investigated. The results show steady increases in the tensile strength and yield strength with increasing partially austenitizing temperature, while the opposite behavior is observed for elongation. The optimum combination including ultimate tensile strength of 746 MPa, impact toughness of 125 J and elongation of 14% is obtained in the dual phase ADI partially austenitized at 810 °C, which is composed of 20% proeutectoid ferrite and 80% ausferrite constituent. Wear behavior could be understood from the manner the hardened layer fragmented and detached. The main wear mechanism under air cooling condition is delamination due to subsurface deformation. Wear rate decreases as matrix hardness increases. According to the results of mechanical and wear tests, dual phase ADI partially austenitized at 810 °C demonstrates superior wear performance as well as relatively reasonable mechanical properties, suggesting the potential of this material for application in metro wheels.