In situ determination of internal stresses in mixed ceramic cutting tools during friction testing using synchrotron radiation

In order to get a better understanding of wear mechanisms in cutting tool materials, the internal stress states caused by complex external thermo-mechanical loads during cutting processes should be investigated. This can be done using in situ X-ray diffraction with high energy synchrotron radiation. For this reason, in first model tests, the strain state in ceramic cutting tool materials (Al₂O₃–Ti(O,C)) for hard turning applications is determined during friction testing. An experimental set-up is presented which allows the measurement of lattice strain tensor components in the major phases of the mixed ceramic material under a two-dimensional loading condition during friction. Results show that during friction almost no lattice strains in lateral direction can be measured due to strain compensation. In contrast, in normal direction, lattice strains increase due to the addition of strains. Stress tensor components are calculated from lattice strains and show higher internal stress states for Ti(O,C) than for Al₂O₃ due to a higher Young’s modulus of Ti(O,C). The set-up represents a major step forward towards future in situ characterization of internal stress states in cutting tool materials exposed to complex thermo-mechanical loading conditions during cutting processes.