Investigating machinability of AISI D6 tool steel using CBN tools during hard turning

Abstract

For machining operation, it is still the challenge to understand the process and selection of cutting tool materials. The motivation for using CBN tools in reconditioning of dies and form tools after useful life which presses for studying critical issues and working for eliminating the costly grinding equipment with CNC turning machine where the job can be completed in one setup. This experimental work involved mechanical characterization of AISI D6 tool steel using low CBN tools based on various analysis; machinability behavior of the tool material and; revealing of CBN tool wear and tool wear mechanisms based on microstructural analysis using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDAX). The novel mathematical models developed are the output response parameters like thrust force, main cutting force, cutting temperature, and surface roughness w.r.t. to variation in cutting speed and feed rate. The parametric analysis study showed that the thrust force, the main cutting force increases with feed. Surface finish improved with feed and the properties and features of tool materials influenced the thrust force and cutting temperature. In case of interrupted hard turning the cutting speed does not affect the main cutting force and thrust force, whereas it has a significant effect on cutting temperature along with feed and inserts grades. Crater wear, micro-chipping, and breakages of cutting edges in continuous turning with abrasion and diffusion being predominant whereas, the worn of interrupted hard turning tools showed crater wear, while abrasion and low intense diffusion are the wear mechanisms affirmed in this study. The novelty of the work is the use of low CBN content brazed tooltips in hard turning as a solution with a low tool acquisition cost without degrading the tool performance and sacrificing productivity.