Surface modification of steels by complex diffusion saturation in low pressure arc discharge

A technique for surface hardening of type 4140 structural steel is proposed. The technique is based on the use of low pressure arc discharges. The complex treatment in one vacuum cycle involves a sequence of operations: ion cleaning of the surface and heating the sample, diffusion surface alloying with aluminum and nitriding. The sample temperature is not over 620 °C at all stages of the process. 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 2.5 in the original state to 13 GPa 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.