https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Thu, 14 May 2026 11:23:14 GMT 2026-05-14T11:23:14Z http://hdl.handle.net/10985/19439 Surface Integrity When Machining Inconel 718 Using Conventional Lubrication and Carbon Dioxide Coolant CHAABANI, Sana; ARRAZOLA, Pedro José; AYED, Yessine; MADARIAGA, Aitor; TIDU, Albert; GERMAIN, Guénaël Surface integrity induced by machining process affects strongly the performance of functional products, for instance, the fatigue life as well as the resistance to stress corrosion cracking. Consequently, it is relevant to evaluate the induced properties on and beneath the machined surfaceto ensure the good performance of the mechanical components while operating under either static or cyclic loads. Furthermore, this is even more important when designing critical components that withstand high loads at high temperatures. In this context, many studies have been carried out in order to characterize the surface integrity (residual stresses, surface roughness, micro-hardness of the affected layer) when machining Inconel 718. However, so far, the cryogenic effect on surface integrity of Inconel 718 is not well established although some preliminary works have already been developed. Therefore, this work aimed to point out the performance of cryogenic machining using the carbon dioxide CO2 as a cryogenic cutting fluid, considering as a reference the conventional lubrication. A comparative study has been carried out during turning operations of Inconel 718 using the same cutting parameters and the same tool geometry. Microhardness measurements showed that the CO2 condition induced higher strain hardening near the surface while conventional condition did not generate notable difference compared to the bulk material microhardness. With respect to residual stresses, results showed that conventional lubrication generated higher tensile residual stress near the surface along the cutting direction when using new tools. As for CO2 cryogenic condition, lower tensile residual stresses have been obtained near the surface. In addition, CO2 condition induced the largest compressive peak when using new and semi−worn tools in comparison with conventional lubrication. Wed, 01 Jan 2020 00:00:00 GMT http://hdl.handle.net/10985/19439 2020-01-01T00:00:00Z CHAABANI, Sana ARRAZOLA, Pedro José AYED, Yessine MADARIAGA, Aitor TIDU, Albert GERMAIN, Guénaël Surface integrity induced by machining process affects strongly the performance of functional products, for instance, the fatigue life as well as the resistance to stress corrosion cracking. Consequently, it is relevant to evaluate the induced properties on and beneath the machined surfaceto ensure the good performance of the mechanical components while operating under either static or cyclic loads. Furthermore, this is even more important when designing critical components that withstand high loads at high temperatures. In this context, many studies have been carried out in order to characterize the surface integrity (residual stresses, surface roughness, micro-hardness of the affected layer) when machining Inconel 718. However, so far, the cryogenic effect on surface integrity of Inconel 718 is not well established although some preliminary works have already been developed. Therefore, this work aimed to point out the performance of cryogenic machining using the carbon dioxide CO2 as a cryogenic cutting fluid, considering as a reference the conventional lubrication. A comparative study has been carried out during turning operations of Inconel 718 using the same cutting parameters and the same tool geometry. Microhardness measurements showed that the CO2 condition induced higher strain hardening near the surface while conventional condition did not generate notable difference compared to the bulk material microhardness. With respect to residual stresses, results showed that conventional lubrication generated higher tensile residual stress near the surface along the cutting direction when using new tools. As for CO2 cryogenic condition, lower tensile residual stresses have been obtained near the surface. In addition, CO2 condition induced the largest compressive peak when using new and semi−worn tools in comparison with conventional lubrication. http://hdl.handle.net/10985/19396 Comparison between cryogenic coolants effect on tool wear and surface integrity in finishing turning of Inconel 718 CHAABANI, Sana; ARRAZOLA, Pedro José; AYED, Yessine; MADARIAGA, Aitor; TIDU, Albert; GERMAIN, Guénaël The most important challenges when machining difficult-to-cut alloys used in critical applications consist mainly in increasing tool life as well as improving the component surface integrity. In particular, the nickel based alloys exhibit very low thermal conductivity inducing higher cutting temperature and thereby rapid tool wear. In this context, cryogenic machining is a promising approach that enhances cooling efficiency either when using the liquid nitrogen LN2 or the carbon dioxide LCO2. According to previous works, cryogenic machining has been carried out on several work materials such as titanium alloys and nickel based alloys. Their findings figured out that longer tool life and better surface integrity were obtained when machining titanium alloys, unlike nickel based alloys. In this work, a comparative study has been carried out in order to investigate the cryogenic machining performance during turning operation of Inconel 718 with respect to tool wear behavior and surface integrity of the machined part. In fact, two cryogenic fluids were employed namely LN2 and LCO2 considering as a reference the conventional lubrication. This study illustrates that conventional lubrication and LCO2 cryogenic cooling allowed to obtain similar machining time, tool wear and surface finish. Nevertheless, LN2 cryogenic machining resulted in the lowest tool life as well as the poorest surface finish. Moreover, residual stresses have been measured beneath the machined surfaces when machining using new tools and tools with different levels of tool flank wear. It was observed that compared to conventional lubrication, both cryogenic conditions showed better results with respect to residual stress profiles along the machined surfaces Wed, 01 Jan 2020 00:00:00 GMT http://hdl.handle.net/10985/19396 2020-01-01T00:00:00Z CHAABANI, Sana ARRAZOLA, Pedro José AYED, Yessine MADARIAGA, Aitor TIDU, Albert GERMAIN, Guénaël The most important challenges when machining difficult-to-cut alloys used in critical applications consist mainly in increasing tool life as well as improving the component surface integrity. In particular, the nickel based alloys exhibit very low thermal conductivity inducing higher cutting temperature and thereby rapid tool wear. In this context, cryogenic machining is a promising approach that enhances cooling efficiency either when using the liquid nitrogen LN2 or the carbon dioxide LCO2. According to previous works, cryogenic machining has been carried out on several work materials such as titanium alloys and nickel based alloys. Their findings figured out that longer tool life and better surface integrity were obtained when machining titanium alloys, unlike nickel based alloys. In this work, a comparative study has been carried out in order to investigate the cryogenic machining performance during turning operation of Inconel 718 with respect to tool wear behavior and surface integrity of the machined part. In fact, two cryogenic fluids were employed namely LN2 and LCO2 considering as a reference the conventional lubrication. This study illustrates that conventional lubrication and LCO2 cryogenic cooling allowed to obtain similar machining time, tool wear and surface finish. Nevertheless, LN2 cryogenic machining resulted in the lowest tool life as well as the poorest surface finish. Moreover, residual stresses have been measured beneath the machined surfaces when machining using new tools and tools with different levels of tool flank wear. It was observed that compared to conventional lubrication, both cryogenic conditions showed better results with respect to residual stress profiles along the machined surfaces http://hdl.handle.net/10985/27041 Udimet 720Li as a potential alternative for optimised aeroengine turbines: Thermophysical and thermomechanical characterisation under wide-ranging testing conditions ORTIZ-DE-ZARATE, Gorka; TIBA, Idriss; MADARIAGA, Aitor; LINAZA, Arantza; GARAY, Ainhara; GERMAIN, Guenael; ARRAZOLA, Pedro J. The need to reduce fuel consumption and emissions is driving advances in aeroengine performance. Efficiency gains are limited by the capacity of the turbine material to withstand the high thermomechanical loads of the combustion process. Nickel-based alloy Udimet 720Li has emerged as a promising alternative to the most widely used Inconel 718 for critical aeroengine components. Nonetheless, its material properties under industry-relevant conditions remain understudied, hindering industrial implementation. Furthermore, discrepancies in the methodology for applying adiabatic heating correction in thermomechanical tests on nickel-based alloys prevent comparability of studies and alloys. This paper presents the thermophysical and thermomechanical properties of forged and heat-treated Udimet 720Li to enable advanced aeroengine design and manufacture. A novel adiabatic heating correction procedure is also proposed for thermomechanical tests. Thermophysical properties (specific heat, density, diffusivity, thermal expansion, and conductivity) were characterised for temperatures 20–1200 °C. Thermomechanical properties were obtained for temperatures 20–1100 °C and strain rates 0.01–100 s-1 with cylinder compression tests. The results show that Udimet 720Li exhibits higher thermomechanical properties than Inconel 718 at elevated temperatures and can withstand greater in-service temperatures (8–23 %) due to the higher γ’ strengthening phase content which remains stable up to 760 °C. Fri, 07 Feb 2025 00:00:00 GMT http://hdl.handle.net/10985/27041 2025-02-07T00:00:00Z ORTIZ-DE-ZARATE, Gorka TIBA, Idriss MADARIAGA, Aitor LINAZA, Arantza GARAY, Ainhara GERMAIN, Guenael ARRAZOLA, Pedro J. The need to reduce fuel consumption and emissions is driving advances in aeroengine performance. Efficiency gains are limited by the capacity of the turbine material to withstand the high thermomechanical loads of the combustion process. Nickel-based alloy Udimet 720Li has emerged as a promising alternative to the most widely used Inconel 718 for critical aeroengine components. Nonetheless, its material properties under industry-relevant conditions remain understudied, hindering industrial implementation. Furthermore, discrepancies in the methodology for applying adiabatic heating correction in thermomechanical tests on nickel-based alloys prevent comparability of studies and alloys. This paper presents the thermophysical and thermomechanical properties of forged and heat-treated Udimet 720Li to enable advanced aeroengine design and manufacture. A novel adiabatic heating correction procedure is also proposed for thermomechanical tests. Thermophysical properties (specific heat, density, diffusivity, thermal expansion, and conductivity) were characterised for temperatures 20–1200 °C. Thermomechanical properties were obtained for temperatures 20–1100 °C and strain rates 0.01–100 s-1 with cylinder compression tests. The results show that Udimet 720Li exhibits higher thermomechanical properties than Inconel 718 at elevated temperatures and can withstand greater in-service temperatures (8–23 %) due to the higher γ’ strengthening phase content which remains stable up to 760 °C.