Martynenko A. Increase of service life of long-length machine parts by way of coating.

The thesis is aimed at increasing the service characteristics of long-length parts in machines and units - rods, shafts and plungers - by way of coating them with electro-spark processing (ESP). An object restoring coating production and strengthening of worn details made from different materials. An aim is selection of effective materials for restoration of worn surface of long-length details and development of parameters of coating which as-sure their high quality and service life and consumer properties. Methods - theoretical-calculation and experimental: x-ray, spectrum, physical-mechanical, chemical, metallo-qrafical researches, wear, corrosive, heat-resistant and commercial tests. A novelty is: - quantitative parameters of mass transfer during ESP depending on processing schedule have been determined. The physical processes controlling structure formation and coating quality have been investigated. - calculated scheme for coating roughness formation has been proposed. It has been found that the most effective material whish assures high service life of restored parts are chromium-containing steels and alloys (10X13, 30X13, ferrochromium) due to high adhesion of coating with the basic metal, properties, uniformity, formation of structures with high hardness, wear resistance, hot strength. - the relation between anode material chemical composition, processing schedule, surface plastic deformation parameters and coating formation kinetics, its thickness, continuity factor and roughness has been established. Requirements for coating obtained by ESP have been formulated; - the parameters of local laser annealing for nitride dissociation at optimum depth have been theoretically justified and experimentally estimated. This treatment assures necessary quality of coating for the parts with previous nitriding. The association be-tween the structure of worn surface and laser treatment parameters for nitrided parts has been found. Commercial test with introduction of the mentioned developments has provided realeconomical effect equal to 139,54 thousand hryvnyas. Industry - machines building.