Performance of oxide PVD-coatings in dry cutting operations

Dry cutting processes effect increased economic efficiency and at the same time fulfil ecological requirements. However, elimination of coolants invol ves absence of their positive influences on the metal cutting process such as lubrication, heat dissipation and chip evacuation. This leads to high ad hesive, abrasive and tribo-chemical tool wear. Innovative oxide coatings me et the sophisticated demands of dry cutting applications such as high wear resistance and the reduction of friction, which minimises the thermal load. The oxide materials provide a high resistance against adhesive wear, due t o the high binding energy. Furthermore, the friction coefficient can be dec reasing with increasing temperature, and a high hardness even at elevated t emperatures is provided. This paper shows the performance of the deposited Al2O3 and ZrO2 coatings in dry drilling of high strength spheroidal graphit e cast iron (SGI70). Influences of the coating composition on the tool wear behaviour, the cutting forces and the chip flow are highlighted. Additiona lly the coatings are evaluated by determination of the absolute temperature on the cutting edge of the drilling tool. Therefore, a suitable measuring technique was developed. (C) 2001 Elsevier Science B.V. All rights reserved .