Formation of a nanostructured CrN layer on nitrided tool steel by low-temperature chromizing

A duplex chromizing process involving the salt bath chromizing of a plasma-nitrided tool steel was carried out at 773 K for 3-24 h. A single-phase CrN layer with a grain size ranging from 20 to 50 nm and an underlying layer consisting of α-Fe and nanosized CrN grains with a grain size ranging from 40 to 80 nm were formed by a 24 h chromizing at 773 K. The duplex chromizing mechanism was discussed.