Akdulum, Aslan; Siyambaş, Yusuf

Hastelloy X superalloy, which exhibits superior performance under harsh conditions such as extreme temperature, oxidation, and corrosion, is widely used in the aviation and energy sectors but causes significant problems in machining due to its difficult machinability properties. This situation has brought up the need for alternative cooling strategies to reduce cutting forces and temperatures during machining, improve surface quality, and minimize environmental impacts. In this research, the impacts of varying cutting variables (depth of cut, feed rate, and cutting speed) on cutting force (FR), surface roughness (Ra), and cutting temperature (T) in the turning of Hastelloy X superalloy under three different machining environments (dry, vortex air, and compressed air) were experimentally investigated. The Taguchi L9 orthogonal layout was utilized for the experimental design, and simultaneous optimization of multiple performance outcomes was carried out by the grey relational analysis (GRA) technique. According to the findings, the lowest FR and Ra occurred in dry, compressed air and vortex air processing environments, respectively. The lowest values in terms of T were obtained in compressed air, vortex air, and dry machining environments, respectively. In summary, the effect of cooling conditions on T was not reflected in FR and Ra. As a result of GRA optimization, where all performance criteria were evaluated together, the most suitable machining condition was determined to be a dry machining environment, an 80 m/min cutting speed, a 0.075 mm/rev feed rate, and a 0.8 mm cutting depth. Vortex air and compressed air environments have been evaluated as a strong alternative to dry environments.

Demirci, Oğuz Kürşat; Erol, Derviş; Gülcan, Halil Erdi

This study evaluates the performance, emissions and enviroeconomic implications of diesel–waste tyre pyrolysis oil (WTPO)–butanol blends in a single-cylinder, direct-injection diesel engine operated at 1500 rpm across 10–50 Nm. Five fuels were tested: neat diesel (D100), D90T10, D80T20, D80T10B10 and D60T20B20. Relative to D100, oxygenated blends incurred a modest fuel-consumption penalty (peak ≈ +8% BSFC), yet delivered pronounced reductions in incomplete-combustion products: carbon monoxide fell by about 50% at high load with D60T20B20. WTPO-only mixtures increased unburned hydrocarbons, whereas adding 10% butanol suppressed HC. Conversely, nitrogen oxides rose by roughly 15–45%, highest for D60T20B20, while tailpipe CO2 decreased slightly (≈4% at 50 Nm). A simple carbon-pricing lens (€70 t-1 CO₂) indicated a ~4% lower carbon-cost component for D60T20B20 than D100 at high load. Considering these trade-offs, D80T10B10 emerges as the most pragmatic configuration, balancing efficiency with air-quality benefits and moderating the NOx rise. The results support partial substitution of diesel by WTPO and butanol where NOx control (e.g., EGR or calibration) is feasible, coupling local pollutant mitigation with incremental decarbonisation and modest cost gains.