Application of MQL and cryogenic CO 2 in thread turning of austenitic stainless steel

Abstract

Thread turning of stainless steel poses significant challenges, as achieving precise threaded components with high productivity and reduced tool wear without flood cooling proves to be a complex task. The application of cooling systems involving Minimum Quantity Lubrication (MQL) and CO₂ can be a sustainable alternative in the machining of difficult-to-cut materials like austenitic stainless steels. This paper analyses the performance of coated carbide tools in thread turning of AISI 304L austenitic stainless steel with a proposed approach that involves exploring sustainable alternatives, particularly focusing on the utilization of MQL stand-alone and a combination of MQL and CO₂ lubricant-cooling system. The impact of these lubricant-cooling systems on the process with different infeed methods (radial, modified flank, and incremental) was investigated. The best results were achieved with the utilization of the MQL+CO₂ system, which led to higher tool life, enabling the machining of 80% more workpieces with radial infeed and 33% more with modified flank and incremental infeed. Moreover, it provided a better surface finish, and lower microhardness on the threaded surfaces by minimizing the adhesion of the workpiece material to the tool and reducing chip deformation. The difference between the microhardness recorded just beneath the surface and the microhardness of the core was reduced by 21.6% for the radial infeed, 26.4% for the modified flank infeed, and 30.5% for the incremental infeed compared to the MQL stand-alone. These findings not only demonstrate the potential for machining performance but also contribute to green manufacturing by reducing the consumption of cutting fluids and minimizing waste.