Effect of different oil-on-water cooling conditions on tool wear in turning of compacted graphite cast iron

Although dry cutting is the most common method used in machining of compacted graphite cast iron (CGI), it sharply reduces the durability of the cutting tool, incurring the need to change tools frequently, and has high operating costs. This work proposes the use of oil-on-water (OoW), specifically external oil-on-water (EOoW), internal oil-on-water (IOoW) and cryogenic air with oil-on-water (CAOoW) droplets, as an eco-friendly cooling method for the turning of CGI. The results show that, because of better combination of cooling and lubrication effect, EOoWrf (spray-to-rake and flank faces EOoW) and IOoW (with 1.2 L/h water content) had the least adhesion on both tool rake and flank faces and the lowest tool wear rate among EOoW and IOoW, respectively. Furthermore, OoW condition and coated tool should be matched in order to carry out the best cutting performance. EOoWrf gave the best tool wear resistance in the machining of CGI by using a CVD Al2O3-based coated tool (Tiger). The penetrability of the OoW conditions depends on machined material, setup conditions of OoW et al. In order to improve the tool resistance in the case of turning CGI, a newly developed OoW condition (CAOoW), was proposed. CAOoW (−50 °C cryogenic air) gave 3 times lower tool wear rate and 0.2-0.3 times lower surface roughness than that of EOoWrf.