The oxidation resistance of the heterophase ZrSi2-MoSi2-ZrB2 powders – Derived coatings

Oxidation Resistance of a Si–TiSi2–MoSi2–TiB2–CaSi2 Coating on a Cf/C–SiC Substrate in High-Speed High-Enthalpy Air Plasma Flows

“…Another potential advantage of increased viscosity along with an increased liquidus temperature is a slight decrease in the vapor pressure of heterogeneous borosilicate films as compared to homogeneous borosilicate glass [35,36]. However, it should be taken into account that the catalytic activity of heterogeneous silicate systems will be higher than that of similar homogeneous ones [13,37].…”

“…The high thickness of the oxide film was associated with a significant fraction of liquid phase in the compact structure at the test temperature. As is known, the liquid phase provides faster mass transfer of reagents, which accelerates the redox processes [13,43,44]. An unoxidized compact was located under the film, represented by the same phases as in the initial state.…”

“…When designing coatings for extreme operating conditions, the concept of self-healing has become widespread [9,[11][12][13], based on the use in the structure of coatings of a glass phase or components capable of glass formation during operation. The glass phase encapsulates the underlying layers and heals microdefects, ensuring the operability of the composition until the nominal supply of glass-forming components is exhausted.…”

“…The role of the healing phase in the inner layers of coatings of the MoSi 2 -Mo 5 Si 3 -HfSi 2 /TaSi 2 /TaC and WSi 2 -W 5 Si 3 -HfSi 2 /TaSi 2 /TaC systems [22], Si-TiSi 2 -MoSi 2 -TiB 2 [11,23], Si-TiSi 2 -MoSi 2 -TiB 2 -SiC w [24], ZrSi 2 /Si-ZrSi 2 /SiC [25] and ZrSi 2 -MoSi 2 -ZrB 2 [13,26] perform eutectics between silicides [22] or between silicon and silicides [11,13,[23][24][25][26]. The presence of eutectics between components in the composition of the coatings improves the adhesion between the layers and to the substrate, accelerates the regeneration of the oxide film, and also to some extent compensates for the differences in the coefficients of thermal expansion of coatings and protected materials.…”

“…The presence of eutectics between components in the composition of the coatings improves the adhesion between the layers and to the substrate, accelerates the regeneration of the oxide film, and also to some extent compensates for the differences in the coefficients of thermal expansion of coatings and protected materials. The effectiveness of the protective action of coatings was confirmed under static oxidation conditions in air at 1650 • C [13,25], in an oxidizing gas flow at 1900 • C [22], in high-speed high-enthalpy air plasma flows at 1850 • C [11,24], 1950 • C [23], 2000 • C [26], and 2200 • C [13], as well as under the conditions of an ablation fire experiment at 2400 • C [25].…”