Effect of secondary hardening on cutting forces, cutting temperature, and tool wear in hard turning of high alloy tool steels

•Effects of secondary hardening on machinability through the measurements of cutting forces, temperature, and tool wear.•In hard turning T15 HSS steel has a high tendency for secondary hardening.•Secondary hardening occurs during machining of the hardened HSS only within a certain cutting speed range (35–60) m/min.•This phenomenon has not appeared during the machining of the D2 tool steel.•Tempering tests and the calculations of the shear plane temperature rise confirmed these results.

Secondary hardening is a phenomenon that occurs during tempering of some alloy tool steels. The effects of such a phenomenon on hard machining have not been investigated yet. The present work demonstrates the effects of secondary hardening on machinability through the measurements of cutting forces, cutting temperature, and tool wear in hard turning T15 HSS, which has a high tendency for secondary hardening. Hardened D2 tool steel has also been machined for comparison.