Ductile Mode Cutting of Tungsten Carbide

Abstract

Cutting experiments are carried out to evaluate the cutting performance of tungsten carbide under nanometer scale chip thickness using a 5-axis CNC machining centre with CBN tools. The cutting forces are measured using a three-component dynamometer. Machined workpiece surface topography, chip formation, and tool wear are examined using an OMIS and SEM. Tool flank wear VBmax is also measured using the OMIS. Surface roughness is measured using a stylus profiler. Experimental results indicate that radial force Fx is much larger than tangential force Fz and axial force Fy. Under different cutting conditions, three types of surfaces of machined workpiece are achieved: ductile mode cutting surface, semi fractured surface and fractured surface. Continuous chips and discontinuous chips are formed under different cutting conditions. Surface roughness increases monotonically when the depth of cut and feed rate being increased. Tool wear occurs mainly on the flank face in ductile mode cutting of tungsten carbide and tool wear mechanisms are dominated by abrasion, adhesion and diffusion wear. SEM observations on machined workpiece surfaces and chip formation indicate that ductile mode cutting is mainly determined by undeformed chip thickness when the tool cutting edge radius is fixed. Ductile mode cutting of tungsten carbide is achieved when undeformed chip thickness is less than a critical value.