Oxygen-Improved Hard Coatings for High Performance Cutting Processes

AbstractConventional hard coatings can be used to improve the properties of tools and machine parts, e.g. to reduce wear and to increase the tool life in cutting processes. In HPC (High Performance Cutting) machining, tools and tool coatings have to show a better thermal and chemical stability due to the higher process temperatures and the higher load of the tools. With oxygen-improved coating systems the thermal or the chemical stability of the used coatings at higher process temperatures can be improved. Therefore, the cutting process can be stabilized. The combination of stable oxidic and oxynitridic structures with conventional hard coatings was used to develop coatings with higher strength and higher hardness as well as an improved stability at higher temperatures. These oxygen-improved hard coatings were produced with the material systems Al-Cr-O-N or Zr-O-N and deposit with an arc-PVD process by use of an oxygen-nitrogen gaseous mixture. According to the analyses, the formation of the cubic and oxidic phases could be verified. These structural elements lead to the improvement of coating properties like hardness and elasticity and optimized thermodynamic properties. The application tests of difficult machinable materials with high strength like ADI (austempered ductile iron) or stainless steel show the great potential of the oxygen-improved hard coatings. In various cutting analyses a strong increase in tool life of oxygenimproved hard coated tools could be proven. This shows the applicability of the developed oxynitridic coating systems for high performance cutting processes to improve the efficiency of cutting processes