Generation mechanism of saw-tooth chip in turning of GH4169 with PCBN tool

Abstract

Superalloys are applied in the aerospace industry, and it is one of classical difficult-to-cut materials, which cause the exacerbation of cutting tool wear. Polycrystalline cubic boron nitride (PCBN) is super-hard cutting tool material, which has a big potentiality in machining superalloys. However, there is no chip breaker on PCBN tool, so that it is difficult to break chip. Therefore, it is very important to research the relationship between the chip generations and both cutting parameters and tool wear for application of PCBN tools. The experiment was done to make sure the relationships cutting force, chip macro-sharp and micro-sharp with the cutting parameter and tool wear. The results demonstrate that the best chip macro sharp can be obtained when v=97 m/min, ap=0.1 mm and f=0.14 mm/r. Also the position of adiabatic shear band and the sequence between two saw teeth of chip based on the result of the test. Then the model of generation of saw-tooth chip is presented: in the process of cutting of GH4169 with PCBN tool, adiabatic shear band is generated when cutting tool is at a point, and then the saw tooth of chip is formed at a next point, after which the next adiabatic shear band can be generated.