Investigation of the effects of cutting tool geometry and coating types on surface integrity in machining of AISI 316L steel

ABSTRACTIn this study the experimental investigation of the effects of the cutting tool geometry (cutting edge form, rake angle and nose radius) and coating types (CVD and PVD) on the surface integrity in machining of AISI 316L steel. In the experiments, different nose radiuses, rake angles, cutting edge forms and cemented carbide cuting tools applied to two different coatings (CVD and PVD) and PSBNR 2525M12 tool holder that has 75° approaching angle according to ISO 3685 were used. Cutting parameters were determined by using four different cutting speeds (125, 150, 175, 200 m/min), three different feed rates (0.1 - 0.2 - 0.3 mm/rev) and two different depths of cut (1.25 - 2.5 mm). The cutting forces occurs during chip removal, surface roughness values on the machined surfaces with residual stresses in machined workpiece were measured and metallurgical structure of the surface layer formed as a result of machining (microhardness and microstructural variations) were evaluated. The surface integrity was evaluated in terms of surface roughness, residual stress, microhardness and microstructure analysis. In all these cutting conditions, it was observed that the surface integrity worsened when the depth of cut and feed rate increased, whereas the surface integrity improved when the cutting speed increased. The best surface integrity results were obtained by the cutting tools which has QM form and the worst surface integrity results were obtained by the cutting tools which has MR form for the CVD coated GC2025 grade, the best surface integrity results were obtained by the cutting tools which has MF form and the worst surface integrity results were obtained by the cutting tools which has MM form for the PVD coated GC1025 grade. When cutting tool nose radius increased, the values of the surface roughness decreased and the values of the others parameters of the surface integrity increased. Generally, when the coated types CVD and PVD were evaluated in terms of the surface integrity, the best performance was obtained by the PVD coated cutting tools. When rake angle increased, surface integrity improved. The best surface integrity was obtained with the cutting speed 200 m/min, feed rate 0.1 mm/rev and depth of cut 1.25 mm, the worst surface integrity was obtained with the cutting speed 125 m/min, feed rate 0.3 mm/rev and depth of cut 2.5 mm.