Pressure and temperature effects on the decomposition of arc evaporated Ti0.6Al0.4N coatings in continuous turning

The isostructural decomposition of arc evaporated Ti0.6Al0.4N coatings at elevated temperatures and high stresses occurring during metal cutting has been studied. Comparisons are made with short time (t = 10 min) anneals at temperatures typical for steel turning operations. The evolution of the spinodal wavelengths is studied by analytical transmission electron microscopy from samples originating from the rake face. Temperature and force measurements during turning allowed for separation of the effects of the temperature and stresses on wavelength evolution. The results show a peak temperature of around 900 °C and a peak normal stress of around 2 GPa during cutting. The overall wavelength is longer after cutting compared to the annealed sample at the same temperature. The results suggest that pressures generated during cutting promote coherent isostructural decomposition which is in line with theoretical studies but for considerably higher pressures.