High-temperature mechanical properties and oxidation resistance of SiCf/SiC ceramic matrix composites with multi-layer environmental barrier coatings for turbine applications

Author(s):  
Qing Hu ◽  
Xin Zhou ◽  
Yunwei Tu ◽  
Xiangrong Lu ◽  
Jingqi Huang ◽  
...  
Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1581 ◽  
Author(s):  
Jianjun Sha ◽  
Shouhao Wang ◽  
Jixiang Dai ◽  
Yufei Zu ◽  
Wenqiang Li ◽  
...  

In order to understand the influence of the mechanisms of ZrC nanoparticles on the high-temperature mechanical properties of C-SiC ceramic matrix composites, the mechanical properties were measured from room temperature (RT) to 1600 °C under vacuum. The microstructures features were characterized by scanning electron microscopy. In comparison with the composites without ZrC nanoparticles, the ZrC-modified composite presented better mechanical properties at all temperatures, indicating that the mechanical properties could be improved by the ZrC nanoparticles. The ZrC nanoparticles could reduce the residual silicon and improve the microstructure integrity of composite. Furthermore, the variation of flexural strength and the flexural modulus showed an asynchronous trend with the increase of temperature. The flexural strength reached the maximum value at 1200 °C, but the highest elastic modulus was obtained at 800 °C. The strength increase was ascribed to the decrease of the thermally-induced residual stresses. The degradation of mechanical properties was observed at 1600 °C because of the microstructure deterioration and the formation of strongly bonded fiber–matrix interface. Therefore, it is concluded that the high temperature mechanical properties under vacuum were related to the consisting phase, the matrix microstructure, and the thermally-induced residual stresses.


2021 ◽  
Author(s):  
Yunze Li ◽  
Dongzhe Zhang ◽  
Zhipeng Ye ◽  
Gaihua Ye ◽  
Rui He ◽  
...  

Abstract Carbon-based nanomaterials mainly including carbon nanotubes (CNTs), graphene, and graphene oxide (GO) have superior properties of low density, outstanding strength, and high hardness. Compared with ceramic reinforcements, a small amount of carbon-based nanomaterials can significantly improve the mechanical properties of metal matrix composites (MMCs) and ceramic matrix composites (CMCs). However, CNTs and graphite always aggregate or degrade during the fabrication with a high temperature, especially in MMCs. GO has the advantages of easier to be dispersed in other materials and better high-temperature stability. Laser directed energy deposition (DED), has been used to fabricate GO-MMCs and GO-CMCs due to the unique capabilities of coating, remanufacturing, and producing functionally graded materials. Laser DED, as a fusion manufacturing process, could fully melt the material powders, which could refine the microstructure and increase the density and mechanical properties. However, GO could react with matrix materials at high temperatures. The survival, degradation, and reactions of GO in laser DED fabricated GO-MMCs and GO-CMCs are still unknown. There is also no investigation on the reinforcement mechanisms of GO in metal matrix materials and ceramic matrix materials in the laser DED process. In this study, GO reinforced Ti (GO-Ti) and GO reinforced zirconia toughened alumina (GO-ZTA) parts were fabricated by laser DED process. Raman spectrum, XRD analysis, and EDS analysis have been applied to investigate the forms of GO in both DED fabricated GO-MMCs and GO-CMCs. The reinforcement mechanisms of GO on microhardness and compressive properties of MMCs and CMCs have been analyzed.


Author(s):  
Karren L. More ◽  
Peter F. Tortorelli ◽  
Larry R. Walker

High-temperature, high-pressure exposure furnaces (commonly referred to as Keiser Rigs) have been used successfully to evaluate the ability of environmental barrier coatings (EBCs) on continuous fiber-reinforced ceramic matrix composites and monolithic Si3N4 to protect the underlying substrate at high temperatures and H2O pressures. The ORNL rig provides for a relatively inexpensive way to conduct high sample throughput, first-stage evaluation of an EBCs protective capability on small ceramic specimens under a range of temperatures, pressures, and H2O contents. The exposure of the EBCs in the Keiser Rig is coupled with extensive microstructural analysis to evaluate EBC failure and degradation mechanisms.


Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 784 ◽  
Author(s):  
Robert Vaßen ◽  
Emine Bakan ◽  
Caren Gatzen ◽  
Seongwong Kim ◽  
Daniel Emil Mack ◽  
...  

Environmental barrier coatings (EBCs) are essential to protect ceramic matrix composites against water vapor recession in typical gas turbine environments. Both oxide and non-oxide-based ceramic matrix composites (CMCs) need such coatings as they show only a limited stability. As the thermal expansion coefficients are quite different between the two CMCs, the suitable EBC materials for both applications are different. In the paper examples of EBCs for both types of CMCs are presented. In case of EBCs for oxide-based CMCs, the limited strength of the CMC leads to damage of the surface if standard grit-blasting techniques are used. Only in the case of oxide-based CMCs different processes as laser ablation have been used to optimize the surface topography. Another result for many EBCs for oxide-based CMC is the possibility to deposit them by standard atmospheric plasma spraying (APS) as crystalline coatings. Hence, in case of these coatings only the APS process will be described. For the EBCs for non-oxide CMCs the state-of-the-art materials are rare earth or yttrium silicates. Here the major challenge is to obtain dense and crystalline coatings. While for the Y2SiO5 a promising microstructure could be obtained by a heat-treatment of an APS coating, this was not the case for Yb2Si2O7. Here also other thermal spray processes as high velocity oxygen fuel (HVOF), suspension plasma spraying (SPS), and very low-pressure plasma spraying (VLPPS) are used and the results described mainly with respect to crystallinity and porosity.


2008 ◽  
Vol 65 (9-10) ◽  
pp. 366-371 ◽  
Author(s):  
P. D. Sarkisov ◽  
N. V. Popovich ◽  
L. A. Orlova ◽  
Yu. E. Anan’eva

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