Effect of zinc chloride for rapid migration of Si in pack siliconizing of copper

Abstract

In a pack siliconizing of copper, ZnCl₂ as an activator showed a peculiar effect to form a thick multi-diffusion layer composed of two diffusion elements of Zn and Si. The Zn was always detected at the edge of the layer and the Si was also detected at just behind the edge. Thus a parallel diffusion of Zn and Si was observed in the siliconizing. The depth of the Si in copper was estimated approximate 50 times than that calculated from the diffusion constant of Si at the same temperature. The diffused Zn was supplied as vapor generated by reaction between ZnCl₂ and ferrosilicon powder. EPMA profile of the layer showed that diffusion of the Si attended the diffusion of the Zn. At 773K the layer of β phase (BCC) was formed with mechanism of linear growth, and α phase (FCC) of the layer was formed at 873K with parabolically. NH₄ Cl as activator was hardly formed diffusion layer in the copper.