POSSIBILITIES OF MODEL WEAR TESTING FOR THE PRESELECTION OF HARD COATINGS FOR CUTTING TOOLS

The wear behaviour of indexible inserts for milling metallic materials was simulated by means of a modified pin-on-disc system. An original indexible insert was used as the stationary specimen (pin), while the rotating specimen (disc) was made of the workpiece material. Physical vapour deposition coatings of TiN, (Ti,Al)N, (Ti,Cr)N, (Ti,Zr)N, Ti(C,N), CrN and ZrN were examined. The discs were made of an Ni-Fe alloy, steel SAE 1045 or copper. The results of the tribological behaviour of the Ni-Fe alloy and the steel SAE 1045 discs agreed satisfactorily in the milling tests and the model wear tests. With copper discs, a significant decrease in the wear of the indexible inserts was only detected in milling tests. By making broader grooves into the copper discs, perpendicular to the sliding direction, the sliding process was periodically interrupted. This change led to a qualitative agreement between the milling and model wear tests. The results reveal that the simulation of the wear behaviour of cutting tools is possible, but the results have to be verified by cutting tests.