Newcomposite coatings, their structure and properties

The effect of structure and phase composition of composite coatings on their service properties under extreme working conditions (high temperatures and pressure, intensive wear by friction, external loads and corrosion environments) was considered. Here, the coatings of Ni-Cr-Si, WC-Co-Cr, Al₂O₃-Ti(Al), ZrSiO₄ systems and others, produced by applying the installation of a multi-chamber detonation of spraying, developed at the E. O. Paton Electric Welding Institute of the NAS of Ukraine, were investigated. To make the detailed analysis of peculiarities of structural-phase state of the investigated coatings (microhardness, volume fraction of pores, phase composition, distribution of dispersed phases, nature of granular, subgranular and dislocation structures), the integrated investigations at all the structural levels were used, namely: optical metallography (Versamet-2, Japan; Leco-M400, USA), analytic scanning (SEM-515 of ''PHILIPS'' company, the Netherlands), as well as transmission microdiffraction electron microscopy (JEM-200CX, ''JEOL'' Company, with 200 kV accelerating voltage, Japan). To evaluate the efficiency of the coatings being investigated under different service conditions, the analytical estimates of structure ↔ properties relations were used. It was shown that the greatest contribution to the properties of strength, ductility and crack resistance of the investigated coatings were made by: dispersion of granular and subgranular structures, uniform distribution of forming strengthening phases of dispersed sizes in absence of lengthy and dense dislocation clusters, being the-concentrators of local internal stresses (potential zones of initiation and propagation of cracks). (author)