EXPERIMENTAL INVESTIGATION AND PERFORMANCE ANALYSES OF CBN INSERT IN HARD TURNING OF COLD WORK TOOL STEEL (D3)

Long-term wear tests on the CBN tool behaviour during hard turning of AISI D3 (60 HRC) have been investigated. The evolution of surface roughness, cutting forces and temperature has been studied according to the cutting parameters and tool wear. Results show that CBN is resistant to wear despite of aggressiveness of AISI D3 steel. A great part of heat generated is mainly dissipated throughout the chip; at a cutting speed of 320m/min the chip temperature is found to be 14 times higher than that recorded in the workpiece. The cutting speed range of 90 to 240m/min has been found suitable to cut this material. The former speed range is appropriate to respect the cutting constraints, whereas beyond 240m/min a drastic increase in tool wear occurs, causing a remarkable drop in tool life. Roughness measurements reveal a dependence on CBN tool wear. However, although the wear rises up to the allowable flank wear of value 0.3mm, roughness Ra remains around 1.0m. The feed rate remains the most affecting factor on the roughness values. The proposed statistical models are based on the response surface methodology correlating the cutting parameters together with roughness, cutting forces and tool life.