Investigation of machining property and sustainability performance of cryogenic turning of GH605 superalloy

Cobalt-based superalloys are widely used in hot-end components of gas turbines due to their excellent elevated temperature mechanical properties. At present, cobalt-based superalloys are usually machined under cutting fluid, which will seriously pollute the environment and harm human health. Cryogenic cutting technology uses liquid nitrogen, supercritical carbon dioxide, etc. as the cooling medium, which has the advantages of environmental protection and energy conservation. In this paper, the cryogenic mechanical properties of cobalt-based superalloy GH605 were investigated, and then the cutting experiments were conducted under three different cooling and lubrication methods (flood condition, cryogenic minimum quantity lubrication, and liquid nitrogen) to investigate the cryogenic machinability and machining sustainability of GH605. The results show that cryogenic temperature can reduce the plasticity of GH605 but has little effect on the compressive yield strength and compressive strength. Compared with the cutting fluid, the cutting force of liquid nitrogen is reduced by up to 72.2%, the cutting-specific energy is reduced by about 83.9%, and the concentration of particulate matter such as PM_2.5 generated during the processing can be decreased by more than 60%. The surface finish and consistency of cryogenic minimum quantity lubrication are better; the surface roughness is reduced by 0.4 ~ 20.4% at different cutting speeds. When the feed speed is greater than 0.10 mm/r, the work hardening degree decreases by 0.8 ~ 19.7%. Under the two cooling strategies, the chip surface is smooth and flat, chip breaking property is improved, but the machining noise is more than 100 dB.