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    Analysis of machinability and sustainability aspects while machining Hastelloy C4 under sustainable cutting conditions
    (Elsevier, 2023) Yildirim, cagri Vakkas; Sirin, Senol; Dagli, Salih; Salvi, Harsh; Khanna, Navneet
    In recent years, developments in the defense, aerospace, and medical industries have significantly increased the expectations regarding material performances. In particular, the demand for materials that can withstand very high and/or very low temperatures and harsh mechanical/chemical conditions has increased. The superior qualities of superalloys can adequately meet this demand. However, the difficulties encountered in the machining of these alloys cause some burdens both ecologically and economically due to the use of cutting fluid. Therefore, the use of cost-friendly and sustainable cutting fluids in the production industry has a vital role, both in terms of machining performance and the environment. From this perspective, this paper focuses on the effects of various cutting environments, i.e., Dry, MQL, LN2, N-2, CO2, Vortex, LN2 + MQL, N-2 + MQL, CO2 + MQL, and Vortex +MQL on the machining performance of Ni-based C4 alloy. Additionally, it was aimed to reveal the effect of cooling/lubrication methods on sustainability by performing a sustainability analysis. Firstly, surface roughness, power consumption, tool wear and mechanisms, and cutting temperature were considered as performance characteristics. When examined in terms of machinability, Vortex + MQL gave the best result in terms of surface roughness and power consumption, while LN2 gave the best result in terms of cutting temperature. Then, a comprehensive sustainability analysis was carried out. As a result, the CESMO follows the order of Dry > MQL > LN2 > LN(2 +)MQL > CO2 > CO2 + MQL > N-2 > N-2 + MQL > Vortex > Vortex + MQL. While employing Vortex + MQL cutting condition, the CESMO decreased by about 11.37% as compared to Dry cutting condition. While using a combination of different sustainable lubrications or coolants, the overall carbon emissions decreased in the range of about 15-25% approximately as compared to the employment of the individual cutting conditions (i.e., coolant/lubricants).
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    The Effect of Environmentally Friendly Cooling Techniques in Hard Turning: Comparison of Nanofluid, Vortex, GQDs and Hybrid Cooling Methods
    (Springer Heidelberg, 2024) Ayhan, Muhammed Omer; Sirin, Emine; Yildirim, cagri Vakkas
    Conventional cutting fluids have negative impacts on the environment, worker health and production costs. Thus, both researchers and manufacturers are doing many studies to obtain alternative methods. The main purpose of these studies is to obtain alternative cooling conditions that are both sustainable and efficient. For this purpose, the current study investigates the effects of different cooling and lubrication techniques on machining performance during hard turning of AISI D3 cold work tool steel. Thus, 10 different conditions such as MQL, vortex tube, graphene-doped nanofluid (GPN), graphene quantum dots doped nanofluid (GQDs) and hybrid cooling conditions including their interaction were applied. The effects of these methods on machining outputs such as surface roughness, cutting temperature, power consumption, flank wear and tool wear characterization were analyzed. Thermal conductivity and pH values were measured to see the relationship between the effect of cutting fluids on machining efficiency and homogeneity/thermal conductivity. The results showed that the vortex + GPN/GQDs hybrid cooling technique gave the best results at all outputs. Compared to dry machining, vortex + GPN/GQDs provided decreases of 53.63%, 49.01%, 56.52% and 46.47% in average surface roughness, cutting temperature, energy consumption and flank wear, respectively.
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    Performance and wear analysis in machining of Co-based Haynes 25/L605 superalloy using sustainable cooling/lubrication agencies
    (Elsevier, 2025) Sarikaya, Murat; Yildirim, cagri Vakkas; Sirin, Senol; Kara, Muhammed Ikbal; Sirin, Emine; Kivak, Turgay; Krolczyk, Grzegorz M.
    The cobalt-based Haynes 25 superalloy is a key material in sectors such as aerospace, medical, and energy, known for its outstanding high-temperature strength, wear and corrosion resistance. However, its low thermal conductivity and rapid work hardening rate make it inherently difficult to machine, highlighting the need for new cooling and lubrication methods. This work investigates the machinability of Haynes 25 under various sustainable cooling and lubrication techniques, including dry conditions, minimum quantity lubrication (MQL), nanofluids, and cryogenic COQ. Additionally, hybrid systems combining cryogenic COQ with nanofluids are also being investigated. The effectiveness of these approaches was ascertained by thorough investigations of surface roughness, cutting temperature, tool wear, and its mechanisms, and power consumption. Experimental results show that hybrid cooling systems especially those including nanofluids and cryogenic COQ significantly improve machining performance. Compared to dry machining, these methods minimized tool wear by 38 % and achieved up to a 44 % reduction in cutting temperature and a 32 % reduction in power usage. These results were a result of the enhanced thermal and tribological characteristics of nanofluids along with COQ's fast cooling capacity. This work provides a route toward sustainable and high-performance manufacture of challenging-to-machine materials by highlighting the possibilities of hybrid cooling strategies to maximize machining efficiency, extend tool life, and lower environmental impact.