Experimental tool wear observation of assisted high pressure cryogenic jet in hard turning process

Abstract

The hard turning process is widely used in automobile and heavy machinery industries. Extreme cutting conditions like high temperature and tool wear rate, are associated with the hard turning process. Cubic boron nitride (CBN) cutting tool is generally preferred for hard machining operations. However, higher tool cost, and tool failure due to thermal shock limits its widespread usage. In machining performance analysis, tool wear is an important parameter which is directly related to the cost of the machining process. Previous studies have reported the improvement in tool life by using cryogenic coolant as a cutting fluid. Objective of this paper is to investigate the effect of cryogenic cooling on the tool wear of CBN and Ti-coated alumina ceramic cutting tools used in the hard turning of AISI 52100 hardened steel. High pressure cryogenic jet (HPCJ) module was optimized and configured to use it for hard turning case. Computational fluid dynamics (CFD) based simulation was used to test and optimize the nozzle design for the flow of cryogenic coolant. It was validated by fundamental heat removal test. Ceramic and CBN cutting tools were then used for hard turning of parts using HPCJ module. Flank wear lengths for various cooling conditions were measured and analyzed. It was observed that the higher tool life of a Ti-coated alumina ceramic can be achieved under cryogenic cooling technique, as compared to the CBN insert under dry conditions. Cost analysis of these hard turning cases was also conducted to check the feasibility of its usage under realistic shop floor conditions. It was observed that the machining using Ti-coated ceramic under cryogenic jet may reduce the total tooling cost compared to CBN cutting tool conducted under dry conditions.