MAX-Phase Structure Formation in Ti–Al–N Coating and Bulk Material During High-Temperature Annealing in Vacuum

The structure and phase state of Ti–Al–N systems obtained in the form of a coating and a bulk material were comparatively studied. The structure was characterized using x-ray diffraction, energy-dispersive spectroscopy (EDS), and Raman spectroscopy (RS). The use of EDS and RS made it possible to verify the x-ray diffraction data on the phase composition of the samples, which is especially important in the study of multiphase Ti–Al–N coatings, and to identify the features of the coating surface microstructure. The Ti–Al–N coating was obtained by chemical deposition of Ti and Al in an N₂ atmosphere on a Ti substrate with subsequent annealing in vacuum at 700, 800, 900, and 1000°C. The bulk Ti–Al–N sample was obtained by reaction sintering of Ti, Al, and TiN powders in vacuum at 1200 and 1300°C. The Ti₂AlN MAX phase appeared in the coating at a lower temperature than in the bulk sample and was characterized by lower thermal stability. The Ti–Al–N coating was characterized by a greater multiphase nature. The phases Ti₂AlN, Ti₄AlN₃, TiN, Ti₂N, and AlN were detected in it after annealing in vacuum at 900°C. The MAX-phase structure was destroyed at 1000°C. The main phase in the bulk sample after annealing in vacuum at 1300°C was Ti₂AlN with a small admixture of TiN and TiAl. The Ti₂AlN MAX phase was destroyed at 1400°C.