Influence of Additives in the Bath and in Iron Specimens on the Composition and Structure of Siliconized Layer Formed on the Specimens by Molten Magnesium Bath with SiC Powder

Abstract

When a molten magnesium bath is used to siliconize iron and steel specimens embeded in SiC powder by keeping them in the bath for 3.6ks at 1123K, the siliconized layer obtained consists of two sublayers; composite and noncomposite layers. The former is composed of Fe₃Si as the matrix and SiC as a dispersed particulate phase, while the latter is only of Fe₃Si.
The effect of addition of about 10 mass% of Ag, Al, Cd, Cu, La, Li, Ni, Pb, Sn and Zn, respectively, to the bath on the composition and structure of siliconized layer was examined in this experiment. Behavior of alloy elements in the steel specimens was also investigated, using pure iron, carbon steels, cast iron and alloy steels.
The addition of Ag and Li, respectively, to the bath, increased the thickness of the layer, while the addition of Al and La decreased the thickness and detered the formation of the composite layer. The addition of the other elements to the bath did not change the thickness, significantly.
The change of the amount of carbon in carbon steels did not affect the siliconized layer, while free carbon in cast iron segregated at the boundary between the siliconized layer and the base iron. Molybdenum and Mn in steels also segregated at the boundary. Chromium and Co could distribute throughout the layer, while W and V concentrated only in the noncomposite layer. Nickel did not dissolve in the layer, but segregated at the surface of specimens. Micro-Vickers hardness was also measured on the siliconized layer of the steels.