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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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    Comparison of VT-20 alloy drilling performance evaluation under dry, MQL, EMQL, and hybrid nanoparticle assisted EMQL ecological conditions
    (Elsevier Sci Ltd, 2024) Khanna, Navneet; Shah, Prassan; Singla, Anil Kumar; Bansal, Anuj; Makhesana, Mayur A.; Sirin, Senol
    The potential of VT-20, a titanium (Ti) alloy in the aircraft industry, is increased as it has stronger thermal capabilities than other pseudo-alpha-Ti alloys. However, the alloy's low heat conductivity and chemical reactivity make machining difficult and necessitate efficient cooling/lubrication. Cutting oils based on emulsion have been used to move heat from the cutting region; however, they are not sustainable due to their negative impacts on workers' health and the environment. Therefore, this novel study investigates alternative lubricating approaches, such as drilling VT-20 alloy under dry, MQL, EMQL, and HNPEMQL conditions using SEM and line-scan EDS analysis. An indigenously developed electrostatic minimum quantity lubrication (EMQL) and hybrid nanoparticles (NPs) immersed in EMQL (HNPEMQL) techniques were utilized to improve drilling performance while reducing cutting oil consumption. Hybrid nanofluids for HNPEMQL application were developed using aluminium oxide (Al2O3) and plate-structured graphene nanoparticles using a two-step process. The surface quality of the drilled hole, tool wear, thrust force, power consumption, hole quality indicators, and microhardness are evaluated. The efficacy of HNPEMQL showed improved drilling efficiency compared to dry, MQL, and EMQL machining. HNPEMQL, EMQL, and MQL conditions reduced tool wear by 102 %, 53 %, and 19%, respectively, to dry drilling. The HNPEMQL condition lowered the thrust force by 75.3 %, 28.69 %, and 18.02 %, respectively, compared to the dry, MQL, and EMQL. HNPEMQL demonstrated a 105 %, 41 %, and 22 % reduced variation in circularity values than dry, MQL, and EMQL for the same number of drilled holes. The findings show that HNPEMQL can be considered a promising cooling and lubricating strategy with improved drilling performance and quality.