Cutting performance and wear behavior of coated cermet and coated carbide tools when turning AISI 4340 steel

This paper presents an investigation on the cutting performance and wear behavior of single coated cermet and multilayer-coated carbide tools with distinct chip breaker geometries (MP and LP) when turning AISI 4340 steel (220 HV). Initially, the temperature of the chips was investigated under cutting speeds of 200, 250, and 300 m min⁻¹, followed by the study of tool wear, wear mechanisms, and machined surface quality under cutting speed of 250 m min⁻¹ using the MP chip breaker only. The results indicated that additionally to the increase in chip temperature with cutting speed, the cermet and the MP chip breaker were responsible for highest chip temperatures. With regard to tool wear, the coated cermet tool showed the largest values for maximum flank wear (VB_Bmax) up to a cutting length of approximately 7000 mm; however, at the end of the test, the cemented carbide presented larger flank and crater wear. Adhesive and abrasive wear mechanisms were observed, respectively, in the rake and flank faces of both tools. Moreover, notch wear and chipping were noticed on the coated carbide tool. Finally, the coated carbide tool provided superior machined surface quality, albeit roughness increased with cutting length for both tools.