Comparison of hot dip aluminised F82H-mod. steel after different subsequent heat treatments

A homogeneous intermetallic phase with a thickness of about 20-30 μm was formed on the surface of the steel F82H-mod. during hot dip aluminising at 700 C for 30 s. The transformation behaviour of this compound Fe2Al5 was investigated by two different heat treatment procedures: the standard heat treatment for F82H-mod. steel (1040 C/0.5 h, 750 C/1 h) and for MANET steel (1075 C/0.5 h, 750 C/2 h). The structure of the transformed coating shows an internal and an external layer separated by a porous band independent of the heat treatment. The internal layer consists of α-Fe(Al), the external of FeAl. On top of the coating a thin alumina layer is observed. The thickness of the internal layer and the phase of the formed alumina layer are influenced by the chosen heat treatment. (orig.)