Lobachova G. Surface hardening of Fe-alloys at Electric-spark alloying by zirconium, titanium, chrome and at Chemical heat treatment

The thesis is devoted to investigation of structural and phase transformations of Fe-alloys surface zone at the Electric-spark alloying (ESA) by transition metals (Zr, Ti, Cr), with varying degrees of carbides and nitrides formation ability at layer-by-layer deposition; at the application of implementation elements containing complex saturating environments (consistently variable nitrogen and carbon atmospheres, liquid environments with the addition of powders Cr3C2, TiC, ZrC, graphite); at the combination with Chemical heat treatment for purposeful control of coatings functional properties. It was found, that proposed treatments contribute to the formation of heterogeneous structure coatings, which include various types of implementation phases, intermetallics, iron based and alloying electrode material based solid solutions, that provides the increasing of microhardness of 3.5 - 10 times and wear resistance of 4 - 14 times compared to untreated surfaces. Combined treatment (ESA in saturating environments + Nitriding; step-by-step Chemical heat treatment + ESA) leads to hardened layers formation depth to 200 m. Qualitative model of structural and phase transformations in the Fe-alloys surface area at the ESA in implementation elements containing saturating environments was proposed. Key words: Electric-spark alloying (ESA), saturate environment, coating, alloyed layer, iron, zirconium, titanium, chrome, Chemical heat treatment.