NEW DEVELOPMENTS IN CHEMICALLY VAPOR-DEPOSITED COATINGS FROM AN INDUSTRIAL POINT-OF-VIEW

The present paper gives an overview of the development of hard and wear-resistant coatings obtained by chemical vapour deposition (CVD), ranging from single layers of TiC, TiN, Ti(CxNy), HfN and Al2O3 to complex multilayer systems using a combination of the hard materials mentioned above. The progress of the performance in general by these and new coatings applied at reduced temperatures is discussed. The introduction of new CVD coating techniques at reduced temperatures and of special substrate materials has improved the performance and increased the application range in dry- and wet-milling and turning operations for Ti(CxNy) and new Al2O3 coatings. A comparison of the performance of moderate temperature CVD Ti(CxNy) coatings vs. different coatings obtained by physical vapour deposition (PVD) in milling applications is given. The wear and the thermal crack behaviour are studied for different cutting conditions and different workpiece materials. For given milling conditions, Ti(CxNy) coatings obtained at moderate temperatures are found to have superior performance. Further improvements to PVD and plasma-assisted CVD can be expected in the near future that will allow exotic materials to be machined by coated tools.