Surface Hardening of Small-Size High-Speed Steel Drills by Chemical Heat Treatment with the Formation of Tungsten Nitrides

The effect of a combined chemical heat treatment process with the saturation of small-size drills made of high-speed steels R6M5 and R6M5K5 with tungsten and nitrogen on the structure of the surface layer and the tool life was studied. Spectral analysis showed that the simultaneous saturation of iron-based drill alloys with tungsten and nitrogen in a pulsed mode produces diffusion layers of different thicknesses containing dispersed inclusions identified as tungsten nitrides. The treatment increases the surface layer hardness. The microhardness at the surface can increase up to 15 GPa, depending on the volume fractions of strengthening nitrides. Surface hardening leads to a substantial increase in the drill life when machining holes in various structural materials.