High Stock Removal Hard Turning of Hardened 52100 Steel with High-Pressure Coolant Applied

Abstract

Hard turning experiments were conducted on hardened 52100 steel utilizing high-pressure (10.3 MPa) coolant. CBN inserts were used. The cutting conditions were investigated to obtain high stock removal with a feasible tool life on the large part hard turning process. A small thermocouple was mounted in a ground slot underneath the CBN insert tip, close to the cutting edge, to effectively measure the insert’s temperature during cutting. The cooling effect of the high-pressure coolant was evaluated by monitoring CBN insert crater wear and the time for the edge to become prematurely fractured. The temperature measurements show that the high-pressure coolant cools the insert more efficiently and has better lubrication capability leading to longer cut time without edge fracture. The study revealed that conventional low-pressure (0.4 MPa) coolant could not economically achieve high stock removal hard tuning due to high cutting temperature leading to premature fracture of the cutting edge. When using the high-pressure coolant and the optimized parameters, the tool life was enhanced by nearly 100%. The machined surface microstructure did not degrade even with the generation of very high shearing and friction heat energy in the cutting zone. Based on validation cut results and production part cycle assessment, the application of high-pressure coolant enables feasibility of high stock removal in hard turning with the ability to improve the productivity of large part rough stage turning by about 46%.