Inconel 718, valued for its remarkable mechanical, corrosion, and high-temperature resistance up to 700 °C, is a predominant material constituting almost half of all global superalloy usage. ...Nonetheless, its exceptional properties make it a challenging material to machine, generating elevated heat at the tool-chip interface that strains cutting tools. Although ceramic tools offer one avenue, cemented carbide tools, particularly in “S” grades, find utilization despite limitations. To render cemented carbide tools viable, a lubricating-cooling medium is essential. Traditionally, abundant cutting fluids or conventional flood application (CFA) are employed. Nevertheless, CFA’s broad use raises sustainability concerns across economic, social, and environmental spheres. To address this, extensive global research aims to explore alternatives or substitutes for CFA. This study introduces an innovative approach using internally cooled tools (ICTs), which eliminates fluid release into the atmosphere, curbing improper disposal. ICT operates within a closed-loop cycle, cooling the tool. Moreover, ICT offers low toxicity for operators, minimizing direct contact risks and workplace contamination. Employing cemented carbide inserts with internal coolant galleries, the ICT method underwent tool life tests during Inconel 718 turning, followed by wear mechanism analyses. The study involved three cutting atmospheres (ICT, CFA, and dry machining (DM)) and two tool coating variations (TiNAl and a double coating AlCrN + TiNAl, referred as AlCrN+). With consistent finishing conditions, cutting speed (
v
c
= 45 m/min), feed rate (
f
= 0.103 mm/rev), and depth of cut (
a
p
= 0.5 mm) remained unchanged. Replicated twice for statistical validity, 18 experiments were conducted. After testing, scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS) unveiled wear mechanisms. Results indicated AlCrN+ surpassed TiAlN coatings, 35% better on average. In contrast, ICT delivered optimal TiAlN-coated tool life, even better than CFA, 27% better. Conversely, AlCrN + coatings achieved the best outcomes with CFA. Irrespective of tool coating or atmosphere, observed wear mechanisms encompassed abrasion, adhesion, and diffusion, with AlCrN+ exhibiting smoother, more uniform wear, predominantly flank, and crater wear. Finally, ICT has shown to be a promising eco-friendly technique with high industrial potential to be explored and improved.
Out of all the mechanical energy generated during material cutting, the majority is converted into heat, raising the temperature at the chip-tool interface, particularly in difficult-to-machine ...materials like Inconel 718, thereby diminishing tool lifespan. Consequently, various lubri-cooling methods mitigate issues related to high temperatures, such as reduced tool life and geometric distortions. The most employed method is cutting fluids application (CFA), but this approach poses several problems, including high cost and environmental and operator hazards. As a result, several techniques have been developed to lower machining temperatures, such as minimum quantity lubrication (MQL), cryogenics, and indirect tool cooling. In this study, an innovative method of tool cooling via internally cooled tool (ICT) was devised and tested. In this approach, the cooling fluid circulates in a closed loop without direct contact with the workpiece or even any fluid dispersion to the atmosphere, increasing environmental appeal and reducing manufacturing coasts. The developed method was compared with temperature measurements taken through thermography and a tool-workpiece thermocouple during the turning of Inconel 718. Two factorial designs studied temperature in Inconel 718 turning via thermocamera and tool-workpiece thermocouple. Additionally, the tool coating (TiNAl or AlCrN + TiNAl), cutting speed, feed, and depth of cut were varied. Using the tool-workpiece thermocouple method, ICT and CFA did not observe any statistically significant temperature difference. However, between ICT and DM, ICT exhibited a lower temperature at the tool-workpiece interface. With thermal imaging, ICT displayed a lower chip temperature than DM. In sum, internally cooled tools emerge as an innovative and environmentally sustainable solution for machining Inconel 718. They offer outstanding heat removal capabilities and substantial advantages over cutting fluids while significantly surpassing the performance of dry machining, thereby addressing crucial concerns in sustainable machining practices.
Superalloys find widespread application in demanding environments owing to their robust strength and high resistance to heat and corrosion. Nonetheless, these very attributes render them ...difficult-to-cut materials. Enhancing machinability necessitates effective lubrication and cooling techniques, the efficacy of which varies depending on the specific alloy, manufacturing methodology, and machining conditions. This exhaustive review presents a fresh analysis elucidating the impact of diverse cooling/lubrication mothods—dry, flood, minimum quantity lubrication (MQL), cryogenic, and high-pressure cooling—on the machining of titanium, nickel, and steel-based superalloys fabricated through conventional and additive manufacturing processes. Key machining operations, including turning, milling, drilling, and grinding, are scrutinized. The ramifications of each cooling approach on critical machinability indicators such as surface roughness, cutting forces, tool wear, temperature, and environmental footprint are meticulously assessed through an extensive literature survey. Both conventionally produced and additively manufactured alloys are scrutinized to discern prevailing trends. The findings underscore the absence of a universally optimal technique across all scenarios. MQL and cryogenic methods exhibit notable efficacy in refining surface finish during titanium alloy machining. High-pressure cooling augments chip breakability and prolongs tool life in titanium machining, albeit yielding disparate outcomes in nickel alloy machining contingent upon wear mode. Additively manufactured alloys generally exhibit superior machinability compared to their wrought counterparts, although warranting further investigation. This holistic analysis furnishes fresh insights into aligning cooling strategies with alloy-process amalgamations to optimize machinability. It identifies extant challenges and avenues for advancing sustainable and efficient machining of difficult-to-cut materials.
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The use of cutting fluids during machining processes remains one of the main challenges toward greener manufacturing, mainly when applied by flooding. The use of vegetable-based cutting fluids stands ...out as one of the alternatives toward more sustainability by making the process eco-friendlier without much impact on the economic aspects of the chain. In this paper, the performance of two vegetable-based cutting fluids applied by flooding was compared to one mineral-based during the turning process of the AISI 1050 steel. They were also tested after aging for microbiological contamination to assess the fluids’ sustainability further. The machinability of the cutting fluids was evaluated by considering the tool life and wear mechanisms, workpiece surface roughness, and cutting temperatures. After microbial contamination, all the fluids increased kinematic viscosity and specific weight, except for the emulsion of vegetable-based fluid, where its kinematic viscosity decreased. The vegetable-synthetic fluid obtained the best machining results in cutting temperature and roughness (Ra) and also had the best behavior for microbial growth. However, considering the tool life, the best result was obtained with the emulsion of the vegetable-based fluid.
Machining is a widely used manufacturing process that involves removing material from a workpiece. During this process, more than 95 % of the mechanical energy from the machine tool's electrical ...motor is converted into heat. This can cause the cutting tool's temperature to soar to extremely high levels, reaching up to 1200 °C or even higher, especially when working with hardened steels. To cool down the machining region, cutting fluids are commonly employed in industries. However, these fluids are not considered sustainable because they pose environmental pollution risks, are costly, challenging to dispose of properly, and can also be hazardous to operators' health. Moreover, in some applications, cutting fluids are not recommended. Considering these issues, this research aims to propose and test a more sustainable approach. The method involves using a closed-circuit system where a mixture of water and ethylene glycol circulates internally in polycrystalline cubic boron nitride (PCBN) tools. These tools are employed in the turning operation of AISI D6 hardened steel and are compared with conventional dry machining. The study utilizes a design of experiment (DOE) and analysis of variance (ANOVA) to plan and analyze the results with statistical reliability. Key output variables considered include cutting temperature, tool life, cutting forces, and surface roughness. The implementation of the internally cooled tool (ICT) system has shown significant benefits. It notably reduces the temperature of the tool's rake face, as measured using a thermographic camera. Despite not being the main variable affecting the maximum temperature, the cooling system plays a crucial role in achieving these improvements. The ICT system also substantially increases the tool life in comparison to conventional dry machining across all tested cutting conditions. While the feed rate remains the most influential factor affecting cutting forces due to increased cutting area, the cooling system also plays a significant role. The ICT system, with reduced temperatures, performs better in this regard. As for surface roughness, the condition of the tool edge emerges as the sole significant factor. Surprisingly, the worn tool provides better surface finishing due to the presence of crater wear. With conventional dry machining, higher cutting temperatures lead to increased tool wear, primarily caused by abrasion and attrition.
•Internally cooled tool (ICT) was used in turning AISI D6 hardened steel with PCBN tools;•An internal cooling system for the sustainable tool has been developed, eliminating the use of cutting fluids;•The tool temperature was reduced, and the machining force increased when using ICT as compared to conventional dry machining;•ICT increased the tool life in all cutting conditions tested;•The ICT system reduced crater wear via lower temperature, with abrasion and attrition as dominant wear mechanisms.
Machining is a process that involves intense heat generation at localized points within the tool-chip interface. This leads to elevated temperatures, which can be detrimental to cutting tools. This ...issue becomes even more crucial when dealing with superalloys like Inconel 718, as they exhibit high shear strength and good creep resistance. Consequently, a significant amount of energy is expended, increasing the cutting temperature. Until now, the primary technique employed to address this issue has been using Cutting Fluids (CFs). In machining, a portion of costs is attributed to fluid handling. It also contains harmful elements that can pose health risks, potentially leading to conditions such as cancer. Moreover, the toxic components can contribute to environmental degradation when improperly disposed of. Therefore, this study proposes an innovative cooling technique called Internally Cooled Tools (ICTs). The ICTs employ an internally circulating coolant fluid through closed cooling channels within the cutting tools, eliminating fluid dispersion into the atmosphere. The main objective was to compare the performance of ICTs in controlling the tool-chip interface temperature during Inconel 718 turning using hard metal tools. For this purpose, a complete factorial experimental design (25) was utilized, with the response variable being the temperature measured by the tool-work thermocouples technique. Beyond that, a sustainable assessment was performed using the Pugh Matrix method. Many key sustainable factors were evaluated related to three atmospheres, cutting fluids in abundance – CFA, dry machining, and ICT. The data base used was a depth literature investigation together with results found in this work. The main findings of this entire work demonstrated that an increase in cutting parameters corresponded to an increase in temperature, as anticipated. TiNAl coating reduced the temperature by up to 10% compared to uncoated tools. Similarly, applying ICTs led to temperature reductions of up to 17% compared to dry machining conditions. The Pugh Matrix made considering 12 factors showed that ICT (14 points) was the most sustainable lubri-cooling method in comparison to CFA (3) and DM (5). Ultimately, ICTs showed to be a promising eco-friendly method. It outperformed conventional methods, showcasing a remarkable heat dissipation capacity. As a result, further studies are warranted to delve deeper into this promising approach.
Thermal analysis of a proposed internally cooled machining tool system França, Pedro Henrique Pires; Barbosa, Lucas Melo Queiroz; Fernandes, Gustavo Henrique Nazareno ...
International journal of advanced manufacturing technology,
02/2023, Letnik:
124, Številka:
7-8
Journal Article
Recenzirano
Due to the increase in environmental degradation, industries are forced to work with less harmful manufacturing means. In machining, it is known that one of the best ways to preserve cutting tool ...life is by using cutting fluids. However, even if this component proves to be effective, its use is still questionable because it strongly contributes to environmental degradation. For many years, several researchers have been looking for new ways to minimize this problem or even eliminate the use of cutting fluids, including the application of coatings in the cutting tool, more ecological coolants or alternative cooling methods. This work presents a thermal study of a proposed cooling technique for machining based on a cutting tool and tool holders designed with internal cooling channels, where a fluid circulates in a closed cycle called internally cooled tool (ICT). It studies the effect that the ICT technique has on the machining temperatures. This proposal can be considered ecologically less harmful because it saves the use of cutting fluids. To investigate the behavior of the system, gray iron was machined using the ICT made of cemented carbide. The response variable was the temperatures generated during cutting, measured by the tool-workpiece thermocouple system and welded thermocouple methods. Input parameters were the cutting speed and machining atmosphere conditions (dry, ICT using water at room temperature and ICT using chilled water). The ICTs reduced up to 21.52% of the temperature at the chip-tool interface compared to the dry machining process and showed a significant impact on the thermal gradients in the cutting tool and tool holder.
High heat generation with the consequent increase in temperature is still a limiting factor for productivity and quality in machining processes, mainly because it strongly affects the tool's life and ...the quality of the workpiece. Cutting fluids in abundance (CFA), often named flood cooling, is the standard machining cooling technique used industrially. However, CFA poses significant environmental hazards while incurring mounting manufacturing costs. To address this, the current paper focuses on a comprehensive performance evaluation of a novel internally cooled tool (ICT) while machining grey cast iron - GCI. Designed and built in-house, the ICT system can internally circulate the coolant through a specifically modified insert, effectively removing the heat from the interface. The machining tests followed a full factorial Design of Experiment- DoE (23) with two quantitative input variables, the depth of cut (doc) (1.0 and 2.0 mm) and the cutting speed (vc) (100 and 150 m/min) and one qualitative variable, the cutting atmosphere (ICT or CFA). The feed rate was maintained constant at 0.1 mm/rev. The response variables were cutting force, tool wear mechanisms, and surface integrity in terms of roughness, microhardness, and microstructure. The main results indicated that, compared to CFA, ICT increased cutting force by 42 %. ICT also increased peak microhardness by 22 % at 500 μm from the top surface. It also induced grain modification at 4 mm depth, indicating that ICT caused a work-hardening effect in the subsurface. These results were an indication that ICT could effectively take heat away at the cutting zone. Statistical analysis on surface roughness showed that the significant variables were the cutting speed and its interaction with the atmosphere, where increasing the cutting speed was the dominant parameter. ICT reduced the roughness at higher cutting speeds, as opposed to CFA. The predominant wear mechanisms were adhesion and abrasion, along with plastic deformation for both ICT and CFA. Finally, the ICT system showed to be a promising eco-friendly technique with high cooling capacity, presenting some advantages compared to CFA, with similar machining performance.
•Machining involves high heat generation and high temperatures limiting productivity.•Cutting fluids in abundance – CFA is the standard Lubri-cooling technique.•Cutting fluids causes the sustainable triple bottom line to be impaired.•Internally cooled tool – ICT is a novel device for eco-friendly machining.•ICT demonstrates high heat removal capacity with some advantages if compared to CFA.
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