Features of Diffusion Interaction in Steel-Aluminum Composite After Explosive Welding and Aluminizing by Melt Immersion

Resumo

Diffusion interaction at an interlayer boundary of St3 steel–AD1 aluminum after explosive welding and aluminizing by melt immersion is investigated. Test heat treatment regimes are revealed providing formation of coatings based on iron aluminides on a steel surface. It is shown that in order to form Fe₂Al₅ intermetallic on a steel surface with the hardness of 10 GPa, an explosion welded steel-aluminum composite must be given double heat treatment. After the first (660 °С, 3 h) a two-layer (Fe₂Al₅ and FeAl₃) diffusion zone is formed, and after the second (640 °С, 3 h) it is destroyed along a main crack between the Fe₂Al₅ and FeAl₃ interlayers. In order to form an Fe₂Al₅ intermetallic coating on a steel surface an aluminized layer obtained by melt immersion must be heat treated at 800 °C. Doping the diffusion zone with Si leads to the appearance of additional phases Al₇Fe₂Si and (Al, Si)₅Fe₃ within the composition, and an increase heat treatment duration leads to a reduction in coating hardness to 7.5–8 GPa.