AISI 12L14 provides excellent machinability, allowing high-performance manufacturing of high-precision parts and brings benefits to the consumers with cost reliability and great material accuracy (single-function) without the need for specific finishing processes. Nevertheless, the effect of the built-up-edge produced during the cutting process are known to be significant in the machining of relatively soft free-cutting metal, which may affect the surface roughness of the workpiece (Mohammad, Ariffin, Baharuddin, Mustapha, & Aoyama, 2017).
AISI 12L14 free machining steels are defined as a specific industrial process used in products such as devices, pipes, connections and pump components in which AISI 12L14 does not have structural liability and therefore certain mechanical characteristics (response to heat treatment, strength and ductility) are called secondary factors (de Almeida et al.
, 2018).
AISI 12L14 free-cutting steel is low-carbon resulfurized with Plumbum adds (0.3% Pb and 0.3%S). The lead in the steel becomes insoluble and the lead molecules are sheared and sprayed over the tool-chip surface during the cutting process.
Lead enhances machinability with less effect on mechanical properties. Because of its poor shear strength, lead works as a good lubricant. Manganese and sulphides support in the forming of the chip and reduce friction and wear of the cutting tool. Free-cutting steels are used where high levels of machining are required as they increase the speed of machining and decrease tool wear (Kulekci, Esme, Kahraman, Ozgun, & Akkurt, 2016)
Generally, coatings can be constructed using various types of materials in several forms and structures. They also consist of single layer, bilayer or multilayer (more than two layers).
However, for microstructure coatings, their structure may vary from a simple single homogeneous structure to more complex systems like alloyed, composite and gradient structures (Khadem, Penkov, Yang & Kim, 2017).
Based on Diciuc & Kazek-K?sik (2017), the use of coatings is anticipated to enhance the productivity and life of the tools. This is because coatings usually give a better preservation of the tool against any dispute such as abrasion and adhesion, diffusion and oxidation other than create a heat barrier for the intensive heat flowing from the cutting area into the tool material. However, in term of heat insulation, it has been justified in the paper that the coatings of continuous cutting tools are not capable to insulate the substrate which result to a vary opinion regarding this matter.
Thin films or coatings are known to be added to structural bulk materials to ensure that the surface properties are improved, particularly in terms of their resistance on corrosion and wear, strength and friction. One of the main research problems for the development of surface engineering is the coatings production. Thus, in contemplation of achieving the objective, they need to make sure that high utility properties of coatings in the area of mechanical characteristics and wear resistance are accomplished. By using PVD processes, simple monolayer, multilayer or gradient coatings are often used in order to provide the known materials a new utility characteristic. In choosing material of the coatings, it is impossible to acquire several properties from an ideal coating instantaneously and the only solution for this issue is by applying nanostructure coatings (Lukaszkowicz, 2010).?
Multi-layer coatings show an efficient performance when they are being used in high-speed machining. This is because they are known to have a high oxidation resistance, high-temperature chemical stability and low thermal conduction compared to others (Xu, An & Chen, 2012).
Grigoriev et al. (2018) have investigated in their study about the multilayer Cr-CrN-(Cr0.35Ti0.40Al0.25)N coating with a nano-structured outer wear resistant layer. In this study, the coating is expected to give a balanced combination of wear resistance, thermostability, resistance to high temperature oxidation and brittle fracture as its result.
Figure 2.1 shows a three-layered architecture of NMCC for cutting tool which consists of 1) wear-resistant outer layer; 2) intermediate layer; 3) adhesive sublayer; and 4) tool material (substrate) According to Vereschaka, Grigoriev, Vereschaka, Popov & Batako (2014), there are three main elements in coating architecture and their functions:
Usually, material that being used for the outer layer must be wear resistant and must have a direct interaction with the material to be machined. This is because it has an essential role in decreasing the physical and chemical activity of the cutting tool material and in declining the adhesion of the task material.
The main function of this element is in supporting the working capacity of the wear resistance in outer layer as well in assisting the enforcement of a strong adhesion with the outer layer and the adhesive sub-layer. Other than that, the intensity of heat flow from frictional heat sources could be reduced when there is an intermediate layer in coating architecture. It could prevent the diffusion processes between the work and tool materials too.
The key function of an adhesive under layer is in providing a strong adhesion between tool material and the coating since this element has a direct contact with the tool material.
Figure 2.1: A three-layered architecture of NMCC for cutting tool.
(Vereschaka et al., 2017)
Adegawa (2007) defined an intermediate layer as “a layer having a function of transferring the pattern of an upper layer to a lower layer by etching process and is provided between an upper layer resist and a lower layer resist.” Therefore, a lower layer pattern with a high aspect ratio should provide to the lower layer primarily by dry etching with the intermediate layer since it can achieve the mask.
According to studies, the establishment of an intermediate layer between coatings and substrates have led to decrease on the mismatch degree of properties among various materials and they also have enhanced the bonding properties of the coating/substrate system. Nowadays, the materials use as an intermediate layer have developed significantly. This can be proven in the use of a monolayer of Ti, TiO2, ZrO2, SiC, or TiN which have been added as an intermediate layer between bioactive ceramic and Ti6Al4V alloy as well as bilayers like TiN/TiO2, ZrN/Zr, and TiN/Ti which also have been used as the intermediate layer. Aside from boosting the bonding strength of the ceramic coating to the Ti6Al4V alloy substrate, these intermediate layers also improve the mechanical properties, wear resistance, and corrosion resistance of the coated Ti6Al4V (Ding et al., 2019).
Today most of products used modern technology to manufacture products which including uses of computer software, hardware and machines in manufacturing industries. The use of CNC or semi-automated control lathe machine seem more significant and reliable for the mass production to maximize speed of product construction with the good quality with precise and consistent dimension and tolerant. Therefore, the used of CNC lathe machine is becoming the crucial part for development of modernized industrialization (Pagar et al., 2016).
The use of a genetic algorithm to handle the CNC lathe by cutting the amount of optimization is efficient. In this article, the idea of putting a simulated annealing algorithm and an evolutionary reaction based on a genetic algorithm is beneficial in optimizing the cutting rate, which not only enhances the algorithm’s consistency but also boosts the algorithm’s optimization accuracy (Chen, 2017).
Lathe machining implies that the metal is separated from the spinning workpiece by a single point cutting tool. This process is characterized by the properties of the workpiece material, the parameters of the cutting tool and the parameters of the tool contact with the workpiece, namely cutting speed, feed rate and depth of cut. Therefore, the cutting method produces a valid workpiece substrate. Consequently, the cutting process provides a certain roughness surface of the workpiece (Ryabov, Kano, Sawada, & Herwan, 2019).
Turning is a machining operation in which a single-point tool eliminates metal from the surface of a spinning workpiece. The tool is fed linearly in a direction parallel to the rotational axis to produce cylindrical design. Turning is typically conducted on a machine tool called a lathe, which generates the power to rotate the component at a certain rotational speed and to feed the part at a specified cut rate and depth.
(Groover, 2010)The simple lathe used for turning and other processes is the engine lathe. It is a flexible machine tool that is manually controlled and commonly used in small manufacturing industry. The headstock includes the drive unit to move the spindle that spins the workpiece. Opposite the headstock is the tailstock in which the middle is placed to protect the other end of the workpiece. The cutting tool is kept in a tool holder attached to a cross-slide, which is mounted to the carriage. The carriage was built to move along the lathe paths due to feed the device parallel to the rotational axis. The ways are like the paths along which the carriage travels, and they are designed with great accuracy to achieve the highest degree of parallelism relative to the spindle axis. The ways were constructed into the base of the lathe, creating a solid frame for the machine tool (Groover, 2010).
The machined parts’ surface finish is a vital criterion and plays a very main role in the manufacturing industries. The surface roughness is a major part of the surface performance. High structure precision and low surface roughness in the machined component will greatly improve the performance, range, efficiency and increase the final production quality. The roughness of the surface affects certain properties of the workpiece such as fatigue strength, creep life, corrosion, wear resistance and etc. Protecting the machined parts from the effects of this negativity is necessary. Thus, it is necessary to control the factors that influence the roughness of the surface There is a clear connection between the surface roughness and cutting parameters like cutting speed, feed rate, depth of cut, etc (?elik, Kilickap, & G?ney, 2016).
The surface quality, expressed in terms of surface roughness, is being used to determine the turning operation efficiency. Different cutting parameters, i.e., cut length, cut speed, and feed rate, is considered to influence the surface roughness (Kandananond, 2010).
According to S et al., (2015), Ilhan Asilturk and Harun Akkus studied the implementations of cutting parameters for turning operations using the Taguchi method to reduce surface roughness (Ra and Rz). The statistical approach of signal-to-noise ratio (SNR) and the analysis of variance (ANOVA) are used to examine the impact on surface roughness of cutting frequency, feed rate and cutting depth. The findings show that the feed rate had the most major effect on Ra and Rz.
From the research by Ramesh, Viswanathan, & Ambika, (2016) on concerning on properties of magnesium alloy AZ91D in dry condition with polycrystalline diamond (PCD) cutting tools when turning operation by using several method such as TOPSIS and grey relational analysis, the stand of the findings is the cutting speed and the rate of feed become influential factors for the measurement of surface roughness and flank tool wear.
Kilickap, Yardimeden, & ?elik, (2017) reported a study by Lebaal et al. that researched a new development based on interpolation and sequential quadratic programming algorithm for Ti-6242S milling operaton using coated
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