Life Cycle Assessment for Rough Machining of Inconel 718 Comparing Ceramic to Cemented Carbide End Mills

Abstract

Nickel-based alloys such as Inconel 718 belong to the group of heat-resistant super alloys. Combined with good mechanical properties over a wide range of temperatures nickel alloys are used extensively in the aero engine sections exposed to elevated temperatures. Besides turbine blades and discs, integrally designed compressor rotors (Blisks) in the high-pressure compressor (HPC) are increasingly made of Ni-alloys. This is the result of an efficiency-driven increase in temperature levels in the rear compressor stages. The machining of these hard-to-machine materials is characterized by low productivity and high tool wear. Compared to the machining with conventional cemented carbide end mills, innovative SiAlON ceramics offer a significant potential to increase the performance of these machining processes while saving cooling-lubricants. Besides an increase in productivity, the evaluation of the overall environmental impact of specific manufacturing processes is gaining importance in the context of more sustainable product life-cycles. This paper focuses on the comparison of different milling strategies in the production of high-pressure compressor rotors made from Inconel 718 in a cradle-to-gate assessment based on DIN EN ISO 14040/44. Thus, the ecological impact of both the state-of-the-art and the novel SiAlON roughing strategy are evaluated considering the consumption of energy, water and compressed air as well as the tool wear. The Life-Cycle-Impact-Analysis (LCIA) will be performed as a midpoint analysis taking multiple indicators into account such as the Global Warming Potential (GWP).