Mechanism of Formation of Aluminum-containing Carbide Layers on Carbon Steel by Al Pack Method

Abstract

The effect of C content in steels on the formation of an Al-containing carbide layer by an Al pack method at 980℃ was investigated. The continuous layer consisting of an outer β-FeAl and inner Fe₃AlC layers was formed on Fe-1.2C (in wt.%) by a short process time. An α-Fe(Al) layer with Fe₃AlC precipitates was formed below the β-FeAl layer on Fe-0.7C after 16 h of process, thereafter an Fe₃AlC layer was formed between the β-FeAl and α-Fe(Al) + Fe₃AlC layers after 25 h. The β-FeAl and α-Fe(Al)+ Fe₃AlC layers were formed on Fe-0.1C, but a continuous Fe₃AlC layer was not developed after longer treatment. A continuous Fe₃AlC layer formed by an Al pack method was explained by carbon enrichment at the α-Fe(Al)/γ-Fe(C) interface due to an inward growth of the α-Fe(Al) layer.