Abstract
Given the development of new heat-resistant nickel alloys that operate at temperatures up to 1,250 °C, as well as the introduction of additive technologies for the production of various parts, it is a relevant task to devise new compositions of highly heat-resistant coatings. Determining the influence of the phase composition of glass-metal-ceramic coatings on its basic properties could improve the effectiveness of protecting those parts that operate under extreme conditions. Therefore, it is promising to conduct a study aimed at establishing the relationship between the microstructure and phase composition of glass-metal-ceramic coatings and the main physical-technical characteristics. This study's results have established that the most high-quality coatings were obtained on the basis of non-crystallizing glass. Such glass is characterized by a temperature coefficient of linear expansion of 92·10-7 degrees-1, a glass transition temperature of 625 °C, and surface tension of 260·10-3 N/m at 850 °C. These properties contribute to the formation of a defect-free coating, providing uniform spreading and high-quality adhesion to the substrate. The resulting optimal coating is characterized by the adhesion strength of 98 %, the thermal resistance (mode 950↔20 °C) of 50 cycles, and the high heat resistance (a weight gain after 100 h in the temperature range of 1,000‒1,050 °C) of 0.03 g/m2·h. Coatings with a minimum amount of glass bonding are distinguished by uniformity and high quality. The optimal ratio of phases "glass:metal-ceramic composition" is 10:90. The structure of the recommended coating is uniform, characterized by the homogeneous distribution of components, the absence of cracks, visible defects, and high quality. The phase composition of the coating after firing is represented by crystals of metallic nickel and silicon, as well as a small amount of residual glass phase.
Highlights
Coatings are artificially created surface layers, which may differ from the base material in chemical and phase compositions, structure, and properties
With an increase in the amount of glass bonding from 10 to 20 wt %, there is a the formation of local areas of the metal and amorphous components, which are aggregated by phase type (Fig. 6)
We have established the influence of the chemical composition of base glasses and composite mixtures based on them on the basic physical-technical properties of coatings
Summary
Coatings are artificially created surface layers, which may differ from the base material in chemical and phase compositions, structure, and properties. Glass-metal-ceramic coatings are heat-resistant and are designed to protect against high-temperature gas corrosion of special nickel alloys [2] The introduction of such coatings makes it possible to improve the quality and reliability of parts operating under extreme conditions as a result of preventing oxidation and burnout of alloying components on the surface and along the boundaries of metal grains [3]. The widespread introduction of glass-metal-ceramic coatings is predetermined by the high manufacturability in comparison with most modern coating methods, which require complex special equipment They are characterized by high adhesion to the protected metal during high-temperature firing, the possibility of applying complex configuration to the overall parts, continuity, slight porosity, high resistance to diffusion of gas medium components, etc. Resolving this issue is a relevant and necessary task
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