Complex Boronized Layer on the Hot-dip Aluminized Steels and Its Surface Performances

Plain carbon steels were dipped in molten aluminum bath at 720°C ±5°C and diffused for 1, 2.5 and 6 hours respectively and then boronized at 950°C for 6 hours. The oxidation, hot-corrosion and abrasion resistance behavior were examined. The experimental results showed the compounds of the aluminized layer, from the surface to the matrix, were composed of Fe2Al5 ( n -phase ) .. Fe3Al ( -phase ) and a phase. The microstructure of aluminized plus complex boronized were similar to that simplex boronized. The XRD analysis results indicated that there existed Fe2B> Fe2AlB2and Fe2Als in this kind of layer. The simplex aluminized layers still remained bright gray appearance when oxidized at 950°C, but complex boronized layer was not able to resist oxidization at the temperature. Both the layers of complex boronized and aluminized had the same anti-oxidization level in the circulative oxidization tests, and also good anti-corrosion ability in molten salt medium. Under dry abrasive conditions, wear resistance of complex boronized layer was superior to the aluminized layer.