Dependence of protective effect of Ti1–xAlxN coatings in 3 wt.% NaCl solution on dissolution mechanism of their phases c‐Ti0.5Al0.5N, c‐AlN, and c‐TiN

Abstract

AbstractThe dissolution mechanism of phases c‐Ti0.5Al0.5N, c‐aluminium nitride (AlN), c‐TiN, and Al2Ti, and elements of the Ti1–xAlxN coatings (for x < 0.6) in 3 wt.% NaCl solution is described based on the results of X‐ray diffraction analysis, energy‐dispersive X‐ray spectroscopy, and scanning electron microscope and previous electrochemical tests. Researchers studied the protective effectiveness of Ti1–xAlxN coatings in 3 wt.% NaCl solution by analyzing the factors: composition, thickness, porosity, total energy of ground state, stresses, structure, and texture. It was first established that the additional c‐TiN phase with Rpmax and Ecormax, and secondary phase Ti0.70–0.82N formed after Al's dissolution in the main phase c‐Ti0.5Al0.5N increases the N content and prevents the Ti dissolution in the Ti1–xAlxN coatings. The phase c‐AlN with icormin reduces the dissolution rate of Al in the c‐Ti0.5Al0.5N phase. The stoichiometric c‐Ti0.5Al0.5N is the most thermodynamically stable phase. The described phase transformations in Ti1–xAlxN coatings during phases dissolution in 3 wt.% NaCl can predict the coating protective effect. A multilayer coating with layers of c‐AlN, c‐TiN, and c‐Ti0.5Al0.5N is recommended for industrial use.