Shcherbovskykh N. Increasing corrosion - erosion resistance chemical machines components generation of a surface layer gradient structure

Object of research is processes of formation of the gradient structure layer surface on the 12Х17Т and 12Х18Н10Т steels by laser surface alloying. The aim of the work is the increasing of corrosion-erosion resistance of chemical machines components constructed from 12H18N10T and 12H17T steels, generation of the surface layers with gradient structure by laser alloying at the expense of the optimal correlation their micromechanical, corrosion - electrochemical properties and wear resistance. The tasks of this work were completely solved by using the fundamental approach of laser surface alloying theory, phase transformation and concepts computer simulation. The microstructure of the surface layers was analyzed by light and electronic scanning microscopy, qualitative and quantitative X-ray energy-dispersive and electron microprobe analyses. The character of structure and fragments size were determined layer-by-layer by recognition of complex-structure objects method. The measurement of the local thermoelectric power and microhardness were made at different depth of the surface layers. The positron annihilation method was used for identification and characterization of the crystal structure defects of these layers. The method of impedance spectroscopy and voltamperometry was used for investigation of their corrosion-electrochemical properties. The wear resistance of the surface layers was examined by syhe tertja. For micromechanical properties determination of the surface layers the microidention method was used. The contact strength was calculated by methods of contact mechanics and computer modeling. The "Expleo" program complex was used to reproduce the absent data of microhardness and thermoelectric power of steels. The monitoring of the corrosion-erosion and micromechanical properties were carried out by neural-network modeling using adapted controller of nechitkoji logic based on networks of geometry transformations. This leads to development of T-Controller User Manual program product. The optimal ratio between the grain size of the plastic matrix and nanostructured conglomerates of the secondary phases (equal to 3,6 - 3,8) was established for the first time. It provides optimal combination of micromechanical, corrosion-electrochemical properties, and wear resistance of the surface layers without losses of plasticity. The further development of the laser alloying regimes and composition of powder mixtures for formation of required structure and phase composition of the surface layers with advanced micromechanical properties. The results of this work were applied in ZAT "Azovskyj machine-building plant", ZAT "Ukrspecmach", TTT "Mashzavod", Chernivci city for increasing the corrosion-erosion resistance of chemical machines components and Lviv Polytechnic National University in education process.