Abstract of Machining of Hastelloy X under dry conditions in term of surface integrity

        Hastelloy-X as an alloy of nickel has been used in the present analysis to determine the impact of different types of machining processes on the environment. along with other parameters, health hazards due to the fluid cutting of Hastelloy-X are analyzed in present research. The research suggests an appropriate solution to overcome the health issues of workers dealing with the fluid cutting of Hastelloy-X is the implementation of dry machining. The JC model is used to determine the surface temperature of the material after dry machining. The consequences of dry machining on the surface of Hastelloy-X are investigated. Based on the analysis it can be concluded that the output of dry machining is much better in terms of cutting temperature, cutting forces, effective stresses, and the surface morphology of Hastelloy-X chip

Keywords: Hastelloy-X, cutting temperature, Cutting fluids, dry machining

INTRODUCTION of Machining of Hastelloy X under dry conditions in term of surface integrity

            Hastelloy-X is a nickel-based alloy and has extensive applications in industries due to higher advantages that are specially related to high-temperature properties. The higher temperature related properties of Hastelloy-X include heat resistance, high melting temperature, ability to retain the mechanical properties as well as chemical properties even at elevated temperature and resistance to erosion, creeping, thermal fatigue, and the thermal shocks (Sofuoğlu, Çakır, Gürgen, & Orak, 2018). Comparing with other superalloys, Hastelloy-X is preferred in the industrial applications particularly in the manufacturing of gas turbine components and engines of spacecraft. Despite significant applications in the industries, the machining of Hastelloy-X is tough. The main issues faced during the machining process of Hastelloy-X is the work hardening and the austenitic matrix (Çakır, Sofuoğlu, & Gürgen, 2018). The issues reduce the efficiency of cutting tools and failure of tools are observed such as craters on the surface, accelerated flank wear, and the notching process observed in the cutting operations. The machining process depends on the suitable parameters such as depth of cut, the speed of cutting and feed rate. The optimum parameter selected for the cutting process leads to longer tool life, higher removal rate for the material and the improved surface finish. In the machining process, the friction produced during between the cutting tool interfaces and the material results in higher temperature and generation of heat that ultimately decreases tool life, dimensional sensitivity of the material, and increases the surface roughness (Shyha, Kuo, & Soo, 2014). In order to overcome the issues, different methods have been devised such as cutting in the presence of fluids, a coating of expensive but suitable materials on the surface and the dry cutting process. The cutting fluids that are metalworking fluids prolong the life of tools but exposure to the cutting fluids can lead to long term and serious consequences such as respiratory disease and hypersensitivity pneumonitis due to the composition of organic and biological contaminants (Çakīr, Yardimede, Ozben, & Kilickap, 2007).

            In the present work, the application of dry cutting is investigated to reduce the hazardous impact on the health of users. The selection criteria along with the process for the dry cutting is investigated for the machining process of Hastelloy-X. The aim of the present work is to propose enough process that reduces the serious health problems faced during machining of Hastelloy-X under dry conditions.

LITERATURE REVIEW of Machining of Hastelloy X under dry conditions in term of surface integrity

                Different methods are devised for the machining of Hastelloy-X that depends upon the cutting tool material, machined workpiece material, and the machining processes. Most of the methods are expensive at the same time the accuracy of the process is restricted due to thermal shocks produced in the material during the machining process (Popke, Emmer, & Steffenhagen, 1999). The suitable conditions for the machining process of the material are proposed in previous researches. The most appropriate alternative in the application of machining is cutting fluids that provide maximum removal rate (Lodhia, 2003). The extensive use of cutting fluid in the machining is due to maximum accuracy in the process. However, the influence of damaging on the environment restricts the use of cutting fluids in the machining of Hastelloy-X.  In order to reduce the environmental and bio-hazards, new approaches are proposed that eliminates the cutting fluid process and the most appropriate technique is dry machining (Sofuoğlu, Çakır, Gürgen, & Orak, 2018). Dry machining of Hastelloy-X is a positive process that can reduce the negative impact of fluid cutting. In research, the cost and amount of fluid were estimated. In 1998 researchers investigated that approximately 2.3 x 109 litter of cutting fluids were used in the machining process of Hastelloy-X. The cost of the operation as $ 2.75 x 109 (Liang, Liu, & Wang, 2018; Çakīr, Yardimede, Ozben, & Kilickap, 2007). Extensive work on the use of synthetic cutting fluids was also carried out to estimate the effectiveness of process when replaced with the cutting fluid process. In the 1970s the negative impact of the cutting fluids on the health of the workers was estimated. The contamination and the constituents of the cutting fluids induce a negative impact on the health of workers. In 1995 Fuchs et al determined the DNA damage process of the workers who were exposed to fluid cutting (Cestari & Yelverton, 1995). The research identified that constant exposure to the contamination increases the breakdown of DNA. Baynes and Reviere (2004) worked on the analysis of Ricinoleic acid (RA) in the cutting fluid and in the skin of workers and they concluded that material diffuses in the body through the skin. The solution to reducing the hazardous impact on the health of users was proposed as dry cutting (Sofuoğlu, Çakır, Gürgen, & Orak, 2018).

METHODOLOGY of Machining of Hastelloy X under dry conditions in term of surface integrity

                Several methods are proposed for the machining of Hastelloy-X such as fluid cutting, dry cutting, hot ultrasonic assisted turning (HUAT), laser micro and macro machining and ultrasonic processes. The ultrasonic assisted turning method the material cutting is based on the vibration generated in the material. The amplitude of vibration increases with the increase in frequency and results in cutting of the material. In the conventional process, the reduced cutting forces are applied on the surface to improve the quality of surface and to reduce the residual stresses generated in the material (Liang, Liu, & Wang, 2018). The cutting process of Hastelloy-X requires considerable life extension, cutting tool working ability, cutting speed, critical speed, and the effect of conventional turning operation. The operation gradually becomes conventional for the cutting process mathematical formalism of the work is mentioned below,

            The present work deals with the biohazards of cutting fluid method and how it can be replaced by the dry method. The dry cutting has both positive and negative impact on the machining of Hastelloy-X (Sofuoğlu, Çakır, Gürgen, & Orak, 2018). The positive impact dry machining process on the machining of Hastelloy-X is a reduction of environmental hazards. In the present research, the proposed methodology for the dry machining of Hastelloy-X is elaborated and the general approach of the process is also considered (Shyha, Kuo, & Soo, 2014). The research can be divided into two subparts including analysis of dry machining of Hastelloy-X and in the second the part the accuracy and surface integrity is evaluated.

Machining of Hastelloy-X

                In the traditional production industry, the machining process is essentially required to improve the quality of the material cutting along with the formation of fine surfaces. There is a number of methods that protect the heating of material and decreases the dimensional sensitiveness of Hastelloy-X. The machining process can be improved by changing the process parameters and the turning operation of Hastelloy-X. The methods developed for the cutting of the material includes fluid cutting, dry cutting, ultrasocial assisted turning, cutting after coating (Sofuoğlu, Çakır, Gürgen, & Orak, 2018). The proper cutting of Hastelloy-X depends on the residual stresses, microcracking, chemical changes in the tool material and the workpiece, tears, changes in the hardness of the surface layer, plastic deformation, and metallurgical transformation (Sofuoğlu, Çakır, Gürgen, & Orak, 2018). The surface integrity changes due to the characterization of machining and milling process. The fluid assisted cutting is hazardous to health, therefore, the dry cutting process can be used to reduce the conventional issues, surface quality, residual stresses, and gradual degradation of the surface. The present work modeled the effect of contamination on health and how it can be controlled (Cestari & Yelverton, 1995).

Surface Integrity of Material

                The research investigated the impact on different parameters on the cutting process and these parameters include the surface integrity of the material after micromachining of Hastelloy-X. The results were predicted by the analysis damage and the temperature of the surface of Hastelloy-X (Sofuoğlu, Çakır, Gürgen, & Orak, 2018). The mathematical model was used to propose the surface roughness after machining. The optimum conditions were selected for cutting the material and to improve the machinability of Hastelloy-X. The numerical investigation worked for the verification of the model for the outputs, morphology of the surface and the chip morphology. The initial temperature of the material was considered as room temperature at 200 C (Sofuoğlu, Çakır, Gürgen, & Orak, 2018). The Cockroft Latham criteria were used for material damage. The shear friction in the modeled material was 0.85 in case of the dry machining of Hastelloy-X.  The model proposes the strain rate modeling and the equation of Johnson Cook model depends on the temperature of the material and the stress generated in the target material (Sofuoğlu, Çakır, Gürgen, & Orak, 2018). The material properties were investigated at different temperature behavior as with increasing the speed of machining the thermal energy of the material increase and consequently the temperature of the material increases. The relation for the surface temperature of the material is mentioned in equation 5 and 6 (Sofuoğlu, Çakır, Gürgen, & Orak, 2018; Skerlos, 2006).

RESULTS AND DISCUSSION of Machining of Hastelloy X under dry conditions in term of surface integrity

Dry machining of Hastelloy-X

            The replacement of fluid cutting with the dry machining of Hastelloy-X is a challenging technique. The process depends on multiple functions simultaneously and depends on the properties of the lubricants, conducting heat, inhibiting zone of cutting, and the nature of the material used for cutting and tool. In the absence of cutting fluid, the temperature of the surface increases due to constant friction and reduced cooling effects. The increase in surface temperature of the material results in the increase of residual stresses, dimensional errors, the building of metal chip on the tool, and poor surface finishing (Razak, Rahman, & Kadirgama, 2014). In the absence of the cutting zone, the higher temperature of the surface leads to the failure of the tool. Several techniques are used to compensate for the requirement of cutting fluids and to cool the surface of the material. The appropriate method for the cooling of the target surface is the internal cooling process during the cutting (Sofuoğlu, Çakır, Gürgen, & Orak, 2018). The cryogenic system, air cooling system, and the thermoelectric system can be used to reduce the tool wear and to keep the temperature of the material at a constant value. The alternation in the material geometry of the material increases the heat removal process and operating temperature increases. The geometry of tools has applications for dry machining. The higher temperature of Hastelloy-X surface leads to hardening of surface and increase in the wear resistance (Razak, Rahman, & Kadirgama, 2014). The chip removal function in the absence of cutting fluid reduces the negative impact on the environment. In order to reduce the scattering of removed particles from the material different types of the tool can be used such as carbide, silicon nitride, cubic boron nitride, and diamond coated tools. The feature of these materials is wearing resistance and high-temperature hardness. The operating condition of these material tends to produce small chips, lower temperature, low cutting forces, and amenable materials. The results show significant improvement in the dry machining and grinding operations. The flushing of Hastelloy-X chips can be handled easily by using vacuum and air systems (Sofuoğlu, Çakır, Gürgen, & Orak, 2018; Çakır, Sofuoğlu, & Gürgen, 2018).

Physical properties of Hastelloy-X

Table 2: Physical properties of Hastelloy-X

Table 3: Parameters used in the JC model along with specific values

Properties of Hastelloy

                Hastelloy-X is basically an alloy consisting of different components at different percentile ratio. Hastelloy-X is widely preferred for the development of components in the combustion region of the gas turbine to high resistibility of thermal shocks even when the temperature exceeds 1100 C for a longer time period of several thousand hours (Razak, Rahman, & Kadirgama, 2014). Hastelloy-X is composed of nickel (Ni), chromium (Cr), molybdenum (Mo) and Iron (Fe). The chemical composition of the alloy is listed below,

Table 1: Percentage composition of Hastelloy-X  (Razak, Rahman, & Kadirgama, 2014)

Environmental impact

                The research conducted by the Environmental protection agency (EPA) of the United States concluded that the metal fabrication process and manufacturing industries are increasing environmental pollution and require modifications in the driving processes. The fluid cutting process is complex but has a wide range of side effect on the employees and workers (Dahmus & Gutowski, 2004). The water-soluble metalworking fluids are composed of a different number of components such as corrosion, lubricants, pH buffers, biocides, defoamers, inhibitors, emulsifiers, and chelating agents. The impact of these particles is on the quality of operation over different time duration and metal working, contamination that are fluid ineffective for the metalworking operations, the burden on the environment, and growth of biocides that induces significant impact on health. Dry machining is a process to reduce the comprehensive side effects of the fluid cutting on the health (Dahmus & Gutowski, 2004; Popke, Emmer, & Steffenhagen, 1999). The characteristic of dry machining is surface texture and the surface finish. The diamond coated tools generate the poor surface finish when cutting the material through dry machining process (Razak, Rahman, & Kadirgama, 2014). The elimination of the cutting fluid from machining of Hastelloy-X increases the tool life, reusing technique, an extension of the life of users and workers (Liang, Liu, & Wang, 2018). In case of the sustainable development process in the manufacturing industry the unique process is used for the identification of environmental performance of the material and process for the development of new strategies and how the social problems of health issues can be resolved by eliminating fluid cutting and by using the dry machining of Hastelloy-X (Skerlos, 2006).

Surface integrity

            The surface integrity of the drilling process depends on the composite and metallic alloy process. The interest of present research is based on the surface integrity by drilling of the metallic composite and engraving of the machined surface. In order to determine the machined surface finishing the innate integrity is required for the analysis of metallurgical, mechanical, topological surface state and chemical state of the surface of Hastelloy-X. In the machining process, surface integrity has prime importance because it reduces the thermal mechanical deformation. The model represents a relation between temperature and strain. The JC model was based on the parameters mentioned in table 2. The parameters used in equation 5 and equation 6 are mentioned in table 3. The increasing trend of surface roughness with increasing the cutting speed is shown in figure 1. On the other hand, the increasing trend in the temperature of the material surface is illustrated in figure 2.

Figure 1: The increasing trend of cutting speed and surface roughness

Figure 2: The increasing trend of surface temperature and cutting speed

CONCLUSION on Machining of Hastelloy X under dry conditions in term of surface integrity

                In the present work, the machining of Hastelloy-X is investigated by different methods. The research contains two main consideration of dry cutting including the environmental effect and impact of dry machining on the surface of the material used in the analysis. The health issues faced by workers by using fluid cutting is also analyzed. The most appropriate method to overcome the health issues of fluid cutting is the implementation of dry machining. The results of the present research find good agreement with the previous researches in terms of cutting temperature and surface roughness analysis. based on results, it can be concluded that cutting forces on Hastelloy-X becomes lower by increasing the speed of cutting. The lowering in cutting forces shows improved accuracy of target surface roughness.