Residual stresses in coatings applied by electric-spark alloying

Abstract

The properties of electric-spark coatings are largely determined by the conditions of electric-spark alloying. Thus, as the energy of the electric-spark pulses increases, the coating becomes thicker but, at the same time, its hardness decreases and its roughness increases considerably. A negative consequence of electric-spark alloying is the appearance of residual tensile stresses. The mechanical properties of coatings subjected to electric-spark alloying were studied in two modes, namely, a {open_quotes}soft{close_quotes} mode with low-energy pulses and a {open_quotes}hard{close_quotes} mode with high-energy pulses. Specimens of U8 annealed steel 70 x 70 x 3 mm in size were alloyed with T15K6 alloy with a modifying admixture in mode II of the EFI-46A installation (Q = 0.12 J, {tau} = 1.8 Msec/m{sup 2}), mode IV (Q = 0.98 J, {tau} = 1.8 Msec/m{sup 2}), and combined modes: first in mode II (Q = 0.12 J, {tau} = 0.9 Msec/m{sup 2}) and then in mode IV (Q = 0.98 J, {tau} = 0.9 Msec/m{sup 2}), and vice versa.