Effects of high-pressure cutting fluid with different jetting paths on tool wear in cutting compacted graphite iron

Abstract

Compacted graphite iron (CGI) is one of the structural materials of internal combustion engines. CGI is very difficult to fabricate by machining. In this paper, on the one hand, dry cutting and cutting fluid with different fluid pressures (pouring, 3–6MPa) are used in machining of CGI to investigate the effects of fluid pressure on tool wear at different cutting speeds (100–300m/min). On the other hand, cutting fluid is jetted in different directions (along rake face and flank face of cutting tool) to investigate jetting path's influences on the wears in the rake face and flank face of cutting tool. Wear morphologies of the cutting tool are analyzed with a 3D display system and scanning electron microscopy (SEM). Wear-reducing effect of the high-pressure (6MPa) cutting fluid is compared with those in the dry cutting, pouring fluid cutting, and low-pressure fluid cutting (3MPa). Influences of fluid pressure variation on cooling and lubricant of cutting fluid in machining are discussed in the final. Results show that the high-pressure cutting fluid has excellent effect on reducing tool wear for both jetting along flank face and rake face of cutting tool. The wear-reducing of cutting tool will be more obvious with the increase of the fluid pressure. Compared with the jetting along rake face, the cutting fluid jetting along flank face can more effectively reduce flank wear. Wear-reducing effect of high-pressure cutting fluid at higher cutting speed is more remarkable than that at lower cutting speed. Crater wear is the main mode on rake face and adhesive and abrasive wear on flank face due to high cutting temperature and hard particles in CGI. The high penetration ability which increases workpiece-coolant contact area and the high convective heat transfer coefficient due to forced heat convection process of the high-pressure cutting fluid enhances its cooling and lubrication effect in machining.