Investigations of surface modification of structural and tool steels treated in low-pressure arc discharges plasmas have been carried out. The complex treatment in single vacuum cycle involved a sequence of operations: ion cleaning of the surface and heating the sample, diffusion surface alloying with aluminum and nitriding. The sample temperature was not over 620 °C at all stages of the process and the total time of treatment was approximately 3 hr. The structure, phase and element constitution, and microhardness of the surface layer have been investigated. It has been established that the significant increase in microhardness from 200–250 in the original state to 1000–1300 kgf/mm2 in the modified layer after complex diffusion saturation in an arc discharge is due to the formation of iron nitride containing dispersed particles of aluminum nitride.

N.V. Strumilova, N.N. Koval, I.V. Lopatin  Formation of hard extensive surface layers by aluminium alloying of structural and tool steels in a low-pressure arc discharge plasma // Физ. мезомех. - 2004. - Т. 7. - № Спец2. - С. 185-188