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The degradation of type 1 aluminized coating during hot stamping leads to the coating cracking due to the formation of a brittle FeAl2 intermetallic phase. The formation of an aluminide coating prior to hot stamping was investigated as a method to simultaneously improve the coating ductility and achieve a good hot corrosion resistance of the hot stamped parts. A formable aluminide coating was obtained when the coating alloying was achieved during the pre-heating of the steel and an Fe content higher than 70 at% (83 wt%) was reached. The coating was identified as Fe3Al phase at room temperature. The formation of this aluminide coating on 22MnB5 hot stamping steel was investigated in detail. The effect of this alternative hot stamping thermal cycle on the room temperature mechanical properties of the steel was also investigated.

The thermo-mechanically induced microstructure changes occurring in a type 1 aluminized coating on hot press forming (HPF) steel were studied in detail. The formation of intermetallic phases at the soaking temperature prior to die quenching revealed that the coating matrix consists mainly of FeAl2 intermetallic phase by the time the press forming carried out. Kirkendall void formation was observed to take place. The thermal oxidation of aluminized coating during HPF was found to be limited, with the coating acting as an effective barrier for the oxygen during heating. The deterioration caused by the high temperature plastic deformation was shown to lead to coating cracking without loss of adhesion. The steel surface was oxidized where it was exposed between the coating segments.