Research On The Corrosion-wear Resistance Of The Novel Fe-cr-b Cast Steels And Their Three-dimensional Interconnected ZrO₂ Reinforced Metal Matrix Composites In Molten Aluminum

Many failures in terms of dies and crucible were caused by the corrosion-wear related to molten aluminum in aluminum industry(such as casting, hot-dip-aluminizing, aluminum alloy composite materials manufacturing). Therefore, it is highly desirable to explore novel Fe-based alloy material with high corrosion-wear resistance.Fe-Cr-B cast steels were prepared successfully by adding B, Cr and Mo alloying elements in a medium frequency induction furnace. The effects of Cr and B on the corrosion resistance and corrosion-wear resistance of Fe-Cr-B cast steels were investigated. Based on the research results of Fe-Cr-B cast steels above, the three-dimensional interconnected ZrO2 was activated by Ni and ZrO2 reinforced metal matrix composites(MMCs) were produced by the traditional sand mold casting technique. The corrosion-wear properties of MMCs were also investigated. The main results were described as follow:(1) Fe-Cr-B cast steels have high corrosion resistance in molten Al. Among them, Fe-12.3 wt.%Cr-5.88 wt.%Mn-3.6 wt.%B-1.89 wt.%Mo(M6) exhibits the highest corrosion resistance to molten Al. The value is 5 times higher than that of H13. It is found thant M2B(M=Fe, Cr, Mo)-type borides play an important role in improving the corrosion resistance of Fe-Cr-B cast steels in molten Al. In details, M2B-type borides can hinder the corrosion of molten Al, and exhibit a much slower corrosion rate than the metal matrix. However, M2B-type borides are corroded at last with the transformation of the Cr-rich Fe2B-type borides into lamellar structures, accompanying with the fracture of Mo-rich Fe2B-type borides. Both of them are embedded in the Fe-Al intermetallic compounds(IMCs) alloyed by Cr and act as root to prevent the corrosion products from falling off effectively.(2) Fe-Cr-B cast steels have high corrosion-wear resistance in molten Al. Among them, the corrosion-wear resistance in molten Al of M6 is 3 times higher than that of H13. The primary Cr-rich Fe2B-type borides play an important role in improving the corrosion-wear resistance of Fe-Cr-B cast steels in molten Al. The the primary Cr-rich Fe2B-type borides, which have excellent corrosion resistance and wear, are higher than the matrix, so they bear the main load during the corrosion-wear test. Due to the corrosion of molten Al is not sufficient, the Fe element in Cr-rich Fe2B-type borides dissolves preferentially from the corrosion layer into liquid Al, resulting in the formation of IMCs containing Cr, Al, and B, and they are broken ultimately under the load.(3) The interface between Fe-Cr-B cast steels and ZrO2 combines well, the corrosion-wear resistance of MMCs is 10 times higher than that of H13. Zr2 O plays an important role in improving the corrosion-wear resistance of MMCs in molten Al. It is found that Zr2 O bears the load and the matrix bears the corrosion of dynamic molten Al during the corrosion-wear in molten Al.(4) As for Fe-Cr-B cast steels and H13, the simple mass loss sum of corrosion and wear is much smaller than that of corrosion-wear in molten Al under the same test conditions. The synergy ratio of Fe-Cr-B cast steels and H13 is larger than 0.8, so the synergism of corrosion and wear is the main reason for the failures of them in corrosion-wear caused by molten Al.