ABRASIVE WEAR BEHAVIOR OF LOWER BAINITE DUCTILE IRON IN CORROSION MEDIA

The corrosion-abrasive wear behavior of lower bainite ductile iron was investigated by corrosion-abrasive wear tests. The main factors of mass loss rate were analyzed. SEM and TEM were used to observe the worn surfaces. The strain-hardening effects beneath the contact surfaces were analyzed by microhardness profiles. The influence of load to corrosion resistance was researched by polarization curves. The results show that the main corrosion wear mechanism was corrosion mass loss and furrow wear. The roughness of worn surface, friction between sample and abrasive, depth of furrow all increased with the test load, which increased the corrosion-abrasive wear rate sharply. Meanwhile, the corrosion micro-cell formed along with the appearance of graphite ribbon and delamination at a higher load, which enhanced the corrosion rate rapidly, and the fracture of delamination resulting from plastic deformation fatigue was another critical factor of the increased mass loss. With the increase of test load, dislocation multiplication and pile-up took place in the retained austenite, which improved the wear resistance of material to some extent. However, the improvement was limited. The average mass loss rate was still increased from 0.16 g/(cm(2).h) to 0.42 g/(cm(2).h) with the increase of test load; the corrosion current density (i) was enhanced from 0.56 mA/cm(2) to 5.62 mA/cm(2) along with the increase of roughness. In addition, the mass loss curves of lower bainite ductile iron were divided into three stages: point contact wear (initial stage), surface contact wear (transition stage) and fatigue wear (stability stage).