Abstract
The austempered ductile iron was austenitized at 900 °C for 1 h and quenched in an isothermal quenching furnace at 380 °C and 280 °C, respectively. This paper aims to investigate the effects of bainite on wear resistance of austempered ductile iron (ADI) at different loads conditions. The micro-structure and phase composition of ADI was characterized and analyzed by metallographic microscope (OM), X-ray diffractometer (XRD) and scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The results showed that the volume fraction of retained austenite in ADI is reduced with the increase of austenitizing temperature. Meanwhile, the two kinds of ADI samples showed varied wear resistance when they were worn at different loads conditions. For wearing at a load of 25 N, the wear resistance of ADI mainly depends on matrix micro-hardness. Thus, ADI with lower bainite structure has higher hardness and leads to better wear resistance. When wearing at a load of 100 N, the increase of micro-hardness of upper bainite was significant. As a consequence, upper bainite showed superior friction and wear behavior. It was also found that the form of wear behavior of ADI changed from abrasive wear to fatigue delamination as the wear load increased from 25 N to 100 N according to the observation on worn surface.
Highlights
Austempered ductile cast iron (ADI) has become an important engineering material because it provides an excellent combination of properties and low cost
The superior mechanical properties of ADI are mainly due to the mixed matrix of bainitic ferrite and carbon-enriched retained austenite, which was obtained by the heat treatment of austenitizing and isothermal quenching
2019, 12, 0.91%, are Figure 2c,d show the typical optical micro-graphs of ADI1 and ADI2 which was austempered at 380 °C and 280 °C, respectively
Summary
Austempered ductile cast iron (ADI) has become an important engineering material because it provides an excellent combination of properties and low cost. The special microstructure provides attractive physical and mechanical properties, such as high tensile strength, ductility, fatigue strength, fracture toughness, and especially, wear resistance [1,2,3,4]. Because of these advantages, ADI has attracted significant attention in recent years due to its wide application in the automotive industry, defense and earth moving machineries, etc. Several studies have been reported to research the wear resistance of austempered ductile cast iron.
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