THE EFFECT OF AUSTEMPERING HEAT TREATMENTS ON THE MICROSTRUCTURE AND CORROSION BEHAVIOR OF CAST IRON IN 3.5% SODIUM CHLORIDE SOLUTION.

Background: Austempered ductile iron (ADI) is an interesting class of materials because of their unique microstructure containing a multiphase matrix (called ausferrite), graphite spheres and oxide inclusions, the need to investigate the effect of austempering heat treatment on corrosion behavior of it. Results: The outcomes demonstrated that heat treatment is very powerful method for improving the corrosion resistance of ductile cast iron. Since the microstructure of the heat treated samples was austempered ferrite. Conclusions: The corrosion resistance of ADI heat treated at (375?C) is higher than ADI heat treated at (325?C) because the microstructural modifications induced by austempering at 375?C which results to a greater coarsening of the austenite grain and broad ferrite needles