Preparation of Fe-Al coating on 316LSS by low-temperature and high-activation pack aluminizing

• The first systematic study on the pack aluminizing of tubular 316 L stainless steel substrates has been conducted. • Low-temperature and high-activity pack aluminizing can achieve the desired coating thickness at lower temperatures and in shorter timeframes. • The coatings prepared by pack aluminizing are uniform and dense. The Fe-Al/Al 2 O 3 composite coating is the preferred tritium permeation barrier system in the current research. The Fe-Al transition layer possesses distinct properties, including excellent thermal adaptability and self-healing capabilities. Pack aluminizing is a widely utilized technique for preparing Fe-Al coatings. In this study, the pack aluminizing process was employed on the surface of 316 L stainless steel substrate, and the effects of aluminizing agent ratio, substrate roughness, substrate geometry, aluminizing temperature and aluminizing time on the growth of the aluminized layer were investigated. The experimental results indicated that the aluminized layer comprises Fe 2 Al 5 and FeAl 3 phases. Increasing the aluminizing temperature and duration resulted in a thicker Fe-Al coating. However, these factors did not significantly affect the phase composition. The geometry of the substrate does not significantly affect the growth thickness and phase composition of the aluminized layer. Based on these findings, the kinetics of the aluminized layer formation process were analyzed. The relationship between aluminizing temperature and coating thickness followed the Arrhenius equation. The activation energy of pack aluminizing on the surface of 316 L stainless steel was determined to be 68.70 kJ/mol under the aluminizing agent ratio of 40 wt.% aluminum, 56 wt.% alumina and 4 wt.% aluminum chloride. The value was found to be lower than the previously reported activation energies. Furthermore, a thicker coating can be achieved at the same aluminizing temperature and duration by increasing the aluminum source and activator content.