THE PERFORMANCE OF HIGH-SPEED STEEL INDEXIBLE INSERTS COATED BY PHYSICAL VAPOR-DEPOSITION IN THE MILLING OF DUCTILE MATERIALS

In recent years considerable developments have taken place in the area of high speed steel cutting tools coated by physical vapour deposition. TiN- and TiCN-coated high speed steel indexible inserts have emerged to fill an important niche in the market where integration into flexible manufacturing systems coupled with the ability to achieve extremely low machining forces and acceptable tool life is demanded. The precoating substrate preparation as well as the coating process itself have not, however, been fully optimized. This is characterized by the large scatter of tool life results obtained when comparing individual corners on any particular insert or indeed when comparing different inserts. In this paper we describe the results of work undertaken to optimize the coating process in order to achieve stable and reproducible performance of TiN-coated high speed steel indexible inserts. Results of tool life tests and investigations into wear mechanisms in the milling of ductile materials are presented and discussed. It has been established that the nature and location of insert clamping in the coating chamber has a direct effect on the performance of the cutting tools. Those inserts located centrally in the coating chamber and oriented with their rake face directed towards the target were found to yield best tool life results.