Application of a low-pressure arc discharge for formation of hard diffusion surface layers

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 2 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 2-1.5 in the original state to 10-13 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.