Supercritical carbon dioxide and minimum quantity lubrication as cutting fluid alternative for grinding (scCO2)

• Applicant: Professor Dr.-Ing. Christoph Herrmann
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549996223

The use of cutting fluids (CFs) is of particular technical importance in grinding processes. At the same time, there are disadvantages associated with the use of conventional CFs and their supply strategies (costs, environmental impact, occupational health hazards). Research projects are therefore investigating alternatives for the use of CFs in grinding processes. A promising alternative is minimum quantity lubrication (MQL), however, the major technical disadvantage of the MQL strategy is the lack of a cooling effect. For this reason, MQL applications are often extended with cooling components, such as cryogenic cooling. Recent research is looking at the combined use of supercritical carbon dioxide (scCO2) and MQL as a CF alternative. The technical advantages such as lower process forces, longer tool life and large cooling effect of scCO2 or a fluid combined with scCO2 have so far been investigated mainly for processes with geometrically defined cutting edge. For processes with geometrically undefined cutting edges, such as grinding, which are particularly dependent on sufficient cooling lubrication, the use of scCO2 offers great research potential. Preliminary work indicates initial findings in terms of lower process forces and reduced energy consumption. A fundamental understanding of scCO2 expansion and resulting machining-relevant parameters such as temperature and beam behavior for different nozzle strategies in grinding is still not known. In addition, an in-depth understanding of the relations of process parameters and structure is lacking. Accordingly, the overall objective of the project is to develop fundamental knowledge on the use of scCO2+MQL in the grinding of different steels using corundum grinding wheels and grinding of a nickel-based alloy with cubic boron nitride (CBN). For this purpose, an in-depth understanding of the process parameters and structure relations when using scCO2+MQL and thus the generation of process know-how for the use in grinding must be developed. The fundamental and systematic investigation of the influence of the designed scCO2+MQL strategy (nozzle design, pressure and temperature ranges, feed into the contact zone, etc.) will be carried out, based on preliminary tests, on surface grinding processes. The experimental investigations will allow a techno-economic evaluation of scCO2+MQL in comparison with flood lubrication during grinding. The underlying mechanisms will be investigated by means of models.

• DFG Programme: Research Grants