Nitride and Carbide Coatings for High Speed Steel Cutting Tools

Abstract

Hard nitride and carbide coatings of Ti, Zr, and Hf were deposited by physical vapor deposition processes on high-speed steel cutting tools to determine their effectiveness in improving the wear properties of the inserts and increasing cutting-tool performance. A collaborative research program involving industrial, university, and government laboratories was established to develop coating processes and tool wear models, to characterize the coating properties and the effect of process parameters on the coaling properties, and to evaluate the cutting performance of coated inserts. Two coating processes were selected for investigation: high-rate reactive sputtering and activated reactive evaporation. The lifetimes of coated inserts were extended 2 to 10 times, depending on the coating composition and process. Analysis of the wear modes that occurred during the cutting tests indicated that the coatings failed by fracture after plastic deformation of the underlying substrate occurred as a result of substrate softening at the high cutting speeds.