Tool steels and high-speed steels are machined with corundum or CBN wheels [LINK09, KONI80]. Carbides and ceramic tools are ground mainly with silicon carbide or diamond wheels. Diamond grit sizes for carbide tool grinding wheels lie commonly between D46 and D181 [FRIE02, p. 46]. Diamond grits with low toughness enable self-sharpening during the grinding process, whereas an irregular shape facilitates good grit retention in the bond [TOML78a]. For the machining of tough carbides and cermets, tendency goes to applying high diamond grit concentrations to have small single grit forces [FRIE02, p. 46]. As consequence, the
grinding wheel wear is low and dimensional tolerances as well as form tolerances of the machined workpieces can be kept constant. Tool grinding operations demand for grinding wheels of complex shapes. Resin bonds have advantages in easy dressability and good damping capabilities because of their soft bonding [FRIE02, p. 53].
4.1.2.3 Surface Grinding Wheels for Turbine Materials
Turbine materials such as Ni — or Al-alloys are highly ductile and produce long chips. The danger of wheel clogging is given and chip formation is characterized by smearing and burr generation. The low heat conductivity of turbine materials leads to heat induced damage of the surface layer in the grinding process. As consequence, grinding wheels for turbine materials stand out by their high porosity. In industry, continuous dressing is applied to sharpen and clean the grinding tool simultaneously to the grinding process.
The so-called Viper grinding method uses high pressure coolant flow to continuously clean and dress the grinding wheel [HILL00, HYAT10]. Highly porous wheels are used. In addition, the carbides and intermetallic phases in turbine materials object the grinding tool to abrasive wear, so that self-sharpening occurs.