Effect of current pulse frequency on the structure and properties of electric-spark alloyed coatings of the Ti - Al - N system

Abstract

ev, T. V. Mosina, and R. K. Ivashchenko UDC 621.726 The mass transfer kinetics, composition, structure, and properties of coatings, formed by high-frequency electric-spark alloying of 45 and 40X steels with the Ti − Al (3:1, 1:1, 1:3) intermetallics and TiN − AIN (1:1) nitride were studied as a function of the current pulse frequency(ν =1200 and 1600 Hz). A decrease in ν was found to lead to a higher mass transfer coefficient and higher microhardness and Young's modulus of the coating as well. This is due to the decrease in the Ti/Al ratio on the surface. The phase composition of intermetallic and nitride coatings differed only insignificantly and did not depend on the value of ν. The main phases of the coatings were Fe − Ti − O and Al − Ti − O solid solutions. The nitride and intermetallic coatings had similar friction coefficients f and wear rates I (f = 0.26 and 0.28, I = 5.4 and 5.9 µm/km), despite the difference in their structure. We can assume that the coating phase composition which defines the composition of the secondary structure under dry friction, is the main factor controlling tribological behavior.