Experimental investigation of the low-temperature oil-on-water cooling and lubrication in turning the hardened AISI D2 steel

In this paper, the influence of the cutting speed, feed, and the depth of cut on the cutting force, surface roughness, cutting temperature, and tool wear were experimentally investigated under the low-temperature oil-on-water (LTOoW) cooling and lubrication condition in turning the hardened tool steel AISI D2 (60 ± 1HRC) with the PCBN cutting tool. The results showed that the three-component cutting forces are FY > FZ > FX. The influence of the cutting speed on the cutting temperature is slightly more visible compared to the feed and depth of cut. In this experiment, a satisfactory surface roughness value of 0.54 µm can be obtained, gaining the effect of the turning instead of the grinding. The flank wear values of the PCBN tool are 142 µm and 148 µm at the cutting speeds of 55 and 140 m/min, respectively; however, the flank wear abruptly increases to 668 µm at a 495 m/min, which has a very serious impact on the tool life. The abrasive wear is considered to be a predominant wear mechanism on the flank wear of the PCBN tool. The rake face is dominated by crater wear due to the high temperature, high pressure, high stress, and high friction at the chip-tool interface. Compared with dry hard turning (DHT) condition, the lower surface roughness value, lower cutting temperature, and longer tool life can be obtained at LTOoW.