In-situ formation of Al-alloyed surface layer on HH309 stainless steel by casting process

A new technique has been suggested to obtain an Al-alloyed surface layer on austenitic stainless steel by casting process. Before casting, the commercial pure aluminum foils with different thicknesses (50-300 mu m) were adequately placed in the bottom of a copper mold, and then HH309 stainless steel melt was cast into this mold. The morphology, structure, composition and magnetic property of the superficial layer are characterized. The results showed that depending on the thickness of the initial foil, the thickness of the surface alloyed layer differ from about 10 to 80 mu m, and its structure is mainly ferrite. The magnetic hysteresis loops indicated that gamma ->alpha transformation in the surface layer creates soft magnetic properties and further layer thickness causes more significant magnetization phenomenon. Also, microhardness measurements revealed a significant increase of hardness in the superficial layer due to the increase of Al content in this layer. The surface layer hardness was from 300 to 480 HV.