## 2 Review of Wear Mechanism in a Grey Cast Iron Machining Process  
Different cutting tools have been used in the machining of gray cast iron. The material from which the tool is made is a fundamental characteristic because it shows the effects of the interactions between the cutting tool and the workpiece [19]. Tool life optimization is a concerning discussion in a machining process, the change of cutting parameters affects the performance of others, and there is a complex relationship. Consequently, the cutting tool characteristics must have superior toughness, hot hardness, thermal shock resistance, oxidation resistance, and affinity with the material to be machined [20]. It is possible to machine with ceramics and PCBN tools with good productivity or quality surface, and the cutting speed parameter can be between 500 and 2000 m/min [21]. The machinability of the PCBN chamfered tool in the dry turning of gray cast iron has been investigated. To evaluate the tool wear mechanism, the cutting parameters were fixed as V\({}_{\text{C}}\) = 204 m/min, ap = 0.4 mm, and f\({}_{\text{n}}\) = 0.2 mm/r for the cutting speed, the depth of cut, and the feed rate, respectively. The main wear mechanisms found were material adhesion and microchipping due to the negative rake angle on the tool chamfer. The embedded material on the flank face suffered severe friction during the cutting process, causing some of the tool material to drop off, and this will chip, forming micro notches. An energy dispersive X-ray spectroscopy (EDX) analysis of the adhered material on the tool confirmed the presence of elements such as Fe, Si, and Mn, which correspond to the composition of gray cast iron [22]. The cutting properties of boron nitride dispersed cemented carbide (BNDCC) inserts that are a hybrid between cemented carbides, and cubic boron nitride (CBN) cutting tools have been analyzed. The tool wear was evaluated during grooving spheroidal cast iron by varying cutting speeds, such as V\({}_{\text{C}}\)\(\leq\) 317 m/min for coated and V\({}_{\text{C}}\)\(\leq\) 176 m/min for uncoated BNDCCs. The results show that adhesion wear predominates in the different types of BNDCC inserts. The build-up edge (BUE) is significantly major in uncoated BNDCC inserts, which is attributed mainly to the high friction in the tool flank-workpiece interface. In comparison, the BUE formation for coated (with TiN and TiAlN) BNDCC inserts is associated with the characteristics of the coating, which increases the coefficient of friction between the chip and gray iron cast [23; 24]. The PCBN cutting tools have been used for the high-speed machining of EN-GJL-250 gray cast iron because they increment the tool life and material removal rate. A paper showed the tool wear mechanisms with PCBN of different compositions and geometry. The cutting data of the tests are: V\({}_{\text{C}}\) = 1300 m/min, f\({}_{\text{n}}\) = 0.5 mm/r, and ap = 0.7 mm. Under these conditions, the results of scanning electron microscope (SEM) observations showed an adhesion layer strongly attached in the tools, which were cleaned by etching in an ultrasonic bath to be certain of the measure of the flank wear. This built-up layer can act as a medium of tool protection during turning [25]. A cemented carbide insert WC-5 TiC-0.5 VC-8 Co (WTVC8) was tested on a machining gray cast iron (HT250). In this case, the wear morphology and EDS analysis conclude that adhesive wear was the principal wear mechanism on the flake face in the cutting tool [26]. A carbide tool SNMA 12408 chemical vapor deposition (CVD), coated with titanium carbonitride, aluminum oxide, and titanium nitride, was tested on machining gray cast iron. For understanding the sulfur influence, the cutting parameters configured were V\({}_{\text{C}}\) = 100, 150, and 200 m/min, f\({}_{\text{n}}\) = 0.257 mm/r, and ap = 2 mm.