Threading of inclusion modified steels with coated carbide tools

An external right hand thread cutting operation was carried out on two grad es of inclusion modified steel in order to investigate the effect of materi al interaction, machinability and the performance of PVD (TiN and Al2O3) co ated inserts with different edge geometry when threading at high speed cond itions. Chipping of the cutting edge, adhesion of flake-like oxide debris o n the worn tool face and thermal cracking of the tool are the major effects of material interaction which adversely affected both the tool performance and the quality of the threaded surfaces. There was also a reduction in ha rdness of the machined surfaces as well as deterioration of the surface qua lity after threading at higher cutting conditions, particularly when the to ol geometry has been altered due to pronounced chipping of the cutting edge . Component forces varied according to the tool geometry and the machining parameters employed during the threading operation. The Al2O3 coated insert s with honed edges gave better overall performance in terms of tool life, l ower cutting forces and lower flank wear rate with little or no adhering fl ake-like oxide debris on the worn tool face. This can be attributed to bett er mechanical and tribological properties as well as a more suitable edge g eometry of the Al2O3 coated inserts relative to the TiN coated inserts with sharp edges.