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.