Barrier coatings for type C/SiC ceramic-matrix composites (Review)

Abstract

The change in the compositions of thermal barrier and antioxidant coatings for C/SiC composite materials was examined. Data are reported on the compositions and properties of bi-, tri-, and multilayer coatings. The mechanism of the barrier effect of several compositions is elucidated. The prospects for use of the new compositions of barrier coatings for increasing the temperature of use of the composite materials are demonstrated.Aviation and space engineering, transport systems, the chemical industry, and thermal and atomic energetics cannot evolve without creating new construction materials suitable for working in extreme conditions -in exposure to high temperatures and pressures, ionizing radiation, dynamic loads, different aggressive media, high gas and liquid flow rates, etc. Such materials are usually created at the same time that methods for protecting them from negative factors are developed.Intensive research has been conducted in the past ten years on developing composite materials based on nonoxide compounds -carbon, silicon carbide and nitride, etc., in which these compounds can be both matrix and reinforcing filler in the form of continuous or separate fibers, whiskers, and plates (C/C, C/SiC, SiC/SiC composites). These materials are distinguished by high strength characteristics, heat resistance, and low weight, which allows using them in aviation and space engineering as high-temperature construction materials, for fabrication of gas turbine, diesel engine, and heat-exchanger parts, and in triboengineering [1,2].In reducing conditions, C/SiC composite materials retain high mechanical property indexes up to a temperature of 2000°C, but in oxidizing conditions, their use is limited by the possibility of oxidation of the carbon at temperatures above 400°C. The SiC/SiC composites were more resistant to high-temperature oxidation due to formation of a barrier layer of SiO 2 on the surface of the composite material. However, in the presence of water vapors, oxidation and volatilization of gaseous products of the reaction are intensified according to the reaction:For this reason, the use of SiC/SiC composites in humid air is limited by temperatures of 1200 -1300°C [3, 4].One possible method for solving this problem is to develop functional barrier ceramic coatings. As a function of the composition of the composite materials, the conditions of their use, and correspondingly the requirements imposed, the coatings can fulfill different functions:improve the mechanical properties of the support in a temperature gradient; limit chemical processes of oxidation and corrosion of the composites; regulate heat transfer at high temperatures of use of the article by changing the thermal conductivity of the material [5].The analytical review by BCC Research reports the results of marketing studies in the North American market for high-efficient ceramic coating technologies in 2004 -2009. It was noted that the total production volume of this kind had $1.1 billion in 2004, and the share of high-strength items was 14%, c...

Self‐Generating High‐Temperature Oxidation‐Resistant Glass‐Ceramic Coatings for C–C Composites Using UHTCs

“…Reports indicate via chemical analysis of UHTC glass layer by, Secondary Ion Mass Spectrometry (ZrB 2 70 vol% +SiC 30 vol% sample) oxidized at 1500°C for 30 min contains <1 wt.% B 2 O 3 , thus making concentrations of B 2 O 3 found within glass after testing at 1600°C less than 1 wt%. Therefore, based on this assumption of limited B 2 O 3 in glass phase, then ZrO 2 cannot remain in solution, as ZrO 2 is not soluble in pure silicates . Thus, final estimated phase chemistry of glass layer formed on bulk 75 vol% ZrB 2 + 25 vol% SiC bulk UHTCs is estimated to be: 14 mol% ZrO 2 particles and 86 mol% SiO 2 glass as indicated on phase diagram (Fig.…”

“…). Remaining porous oxide scale is ZrO 2 with B 2 O 3 liquid wicking from bulk and mixing with SiO(g) which condenses to SiO 2 (l) at surface during dynamic continuous oxidation …”

“…A number of dense ceramic coatings have been developed that are applied on top of C–C composites for oxidation resistance; however, underlying C–C will experience oxidation if protective coating is compromised. Oxide glass coatings on C–C have been used at low temperatures (1000°C–1200°C), and SiC‐based coatings have been used at higher temperatures such as on former space shuttle, however, they are limited to ~1500°C due to active SiC oxidation …”

“…A number of dense ceramic coatings [2][3][4][5][6] have been developed that are applied on top of C-C composites for oxidation resistance; however, underlying C-C will experience oxidation if protective coating is compromised. Oxide glass coatings on C-C have been used at low temperatures (1000°C-1200°C), [7][8][9][10][11] and SiC-based coatings have been used at higher temperatures 5,[12][13][14][15][16][17] such as on former space shuttle, 6,18,19 however, they are limited to~1500°C due to active SiC oxidation. 1,[20][21][22][23][24][25] Ultra high-temperature ceramic (UHTC) additions to C-C composites and SiC fiber composites are of interest because they show exceptional thermal stability and produce glassy oxides that inhibit oxygen diffusion.…”

Thermal cycling behavior and hot corrosion performance of the plasma sprayed Er2Si2O7coatings deposited on Cf/SiC composites

“…The remedial approach to counter such a threat is to use a suitable coating against the oxidation, high temperatures and erosion. Various kinds of protective coatings have been reported recently in literatures [6][7][8].…”