Failure mechanisms of physically vapour deposited coated hardmetal cutting inserts in turning

Abstract Thin hard physical vapour deposition (PVD) coatings attribute excellent cutting performance to cemented carbide inserts, allowing a beneficial exploitation of modern CNC machine tools. Based on the continuous chip formation, coatings experience distinct failure mechanisms in turning. To clarify the influencing parameters on coating wear resistance release, turning experiments with TiAlN derived coatings, deposited on cemented carbide inserts have been carried out. At a variety of cutting speeds, the experimental results are explained through analytical ones obtained by means of finite elements method (FEM) calculations indicating a coating static decohesion at low cutting speeds, owing to its overstressing. On the other hand, at higher cutting speeds tribomechanical abrasive phenomena are dominant. Nevertheless, the cutting accomplishment of coated tools is impressive, in as much as even after the local initiation of coating failures the tool still exhibits adequate cutting reserves, continuing its severe service up to the end of its operational life due to abrasive flank wear. As the overall cutting length increases theoretical and experimental results show that a progressive local coating decomposition occurs while the cutting forces remain practically stable. Herewith chip formation alterations such as a gradual increase of the chip compression ratio and a consequent reduction of the tool contact stresses are induced.

[1]  B. Karpuschewski,et al.  Performance of oxygen-rich TiALON coatings in dry cutting applications , 1998 .

[2]  Konstantinos-Dionysios Bouzakis,et al.  The concept of an advanced impact tester supported by evaluation software for the fatigue strength characterization of hard layered media , 1999 .

[3]  Fritz Klocke,et al.  Improved Cutting Processes with Adapted Coating Systems , 1998 .

[4]  Konstantinos-Dionysios Bouzakis,et al.  Determination of the fatigue behaviour of thin hard coatings using the impact test and a FEM simulation , 1996 .

[5]  Konstantinos-Dionysios Bouzakis,et al.  Fatigue failure mechanisms of multi- and monolayer physically vapour-deposited coatings in interrupted cutting processes , 1998 .

[6]  W. König,et al.  New Approaches to Characterizing the Performance of Coated Cutting Tools , 1992 .

[7]  T. Leyendecker,et al.  Experimental and FEM Analysis of the Fatigue Behaviour of PVD Coatings on HSS Substrate in Milling , 1998 .

[8]  T. Kitagawa,et al.  Analytical prediction of cutting tool wear , 1984 .

[9]  Fritz Klocke,et al.  Coated Tools for Metal Cutting – Features and Applications , 1999 .

[10]  Konstantinos-Dionysios Bouzakis,et al.  Quantification of properties modification and cutting performance of (Ti1-xAlx)N coatings at elevated temperatures , 1999 .

[11]  J. Georges,et al.  Vickers Indentation Curves of Elastoplastic Materials , 1985 .

[12]  M. Weck,et al.  Application of low temperature PVD coatings in rolling bearings: tribological tests and experiences with spindle bearing systems , 1996 .