PVD-coating of electroplated cBN grinding tools to optimize the wear and application behavior when grinding nickel-based alloys

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This project aims to decrease the grinding wheel wear and to increase the material removal rate when grinding nickel-based alloys by applying coatings. Due to their excellent high-temperature strength, high fatigue strength, and exceptional corrosion resistance, nickel-based alloys are used in high-tech areas such as in turbines and engines. The required surfaces with low roughness can often only be manufactured by grinding. Grinding nickel-based alloys is difficult because of their thermal, mechanical and chemical properties. The reduction of the grinding wheel wear as well as the generation of a high quality surface and near surface integrity are the challenges. The friction between grinding wheel and workpiece during the process leads to mechanical wear and the heat from friction accelerates the chemical and thermal wear. The application of coatings on grinding wheels is a promising method to meet the mentioned challenges. By using coatings, the friction will be reduced and the grain retention force will be increased, whereby a bigger chip space is possible via reduction of the galvanic bond thickness. There is still a lack in understanding the interdependencies between the coating process parameters and the process results. At the end of the project, a reduction of tool wear and friction as well as an increase of the chip space and the involved optimization of the martial removal rate when grinding nickel based alloys with PVD-coatings will be achieved. A PVD-coating will be developed that increases the grain holding forces and improves the tribological and non-adhesive properties of the grinding wheel. The chip space will be maximized by a reduced bond level of the cBN grains because of the improved galvanic bond properties of the applied PVD-coating. The grain retention forces applying different PVD-coatings and bond levels will be examined. The advantage of the PVD-coating will be validated in an experimental comparison of coated cBN-grinding wheels with adjusted chip space against non-coated cBN-grinding wheels with standard chip space at high efficiency deep feed grinding of nickel based alloys. The project result will be a coated grinding wheel with adjusted chip space and larger space for cooling lubricant and chips in process. As a consequence, the material removal rate and the total material removal when high efficiency deep feed grinding nickel-based alloys will be increased without thermal damage of the near surface layer. The grinding wheels’ performance and the efficiency of the process will be increased.