25. YbB4 Modified SiCf-SiC Enhanced Water and Oxygen Corrosion Resistance of Composite Materials

Digital Object Identifier ：10.1016/j.ceramint.2023.08.354

Laboratory of Thermal Structural Composite Materials Science and Technology, Northwestern Polytechnical University Researcher Wang Jing The team published in the journal « Ceramics International 》published a paper titled “ Y/YbB4-Modified SiCf/SiC Composites with Enhanced Water-Oxygen Corrosion Resistance ” of the paper. Mainly studied Y/YbB₄ Modified SiCf/SiC The corrosion resistance of composite materials in high-temperature water–oxygen environments, and comparison with traditional CVI-SiCf/SiC A comparison was made of composite materials. 。

Research Background

SiCf/SiC Composite materials are lightweight, high-strength, high-temperature structural materials widely used in the thermal structural components of aeroengines. However, when they operate in high-temperature environments rich in water vapor, Silicon carbide Generated by matrix oxidation Silicon dioxide It reacts with water vapor to form volatile silanols. Si(OH)₄ This substance is easily carried away by high-velocity gas flows, leading to rapid material corrosion, performance degradation, and even structural failure.

This study is the first to propose the use of Y/YbB₄ Synchronous Modification SiCf/SiC A novel composite material with low porosity, high density, and excellent resistance to water and oxygen corrosion has been fabricated via a combined process of slurry impregnation and reactive melt infiltration.

Research Methods

1. Preparation of Porous SiCf/SiC Preform
2. Y/YbB₆ Introduction of Resin Carbon
3. Si-Y Alloy reaction infiltration

Water Oxygen Experiment

In 1200 Under high temperatures of ℃, 50 vol% H ₂ O + 50 vol% O ₂ The flow rate of the water-oxygen mixture is 20 mL/min , the experimental times are as follows: 1，5，10，25，50，100h。

Protection Mechanism

1. Physical barrier effect: the dense matrix impedes the penetration of water and oxygen.
2. Chemical protective layer: a stable layer formed during the corrosion process Y/Yb Silicates inhibit further matrix corrosion.

Research Results

1. Successfully prepared with low porosity ( 3.2% ）、 highly dense Y/YbB₄ Modified SiCf/SiC Composite materials, employing SI+RMI The process achieves effective matrix modification.
2. Significantly enhanced resistance to water and oxygen corrosion, 1200°C Corrosion 100 h Post-strength retention rate of 76.84% , compared with the traditional CVI Enhancement of process-composite materials 15.71% 。
3. The material retains pseudo-plastic fracture behavior after corrosion, indicating that the modification does not compromise its toughness and making it suitable for high-temperature, high-humidity service environments.
    

High-Temperature Static Water-Oxygen Corrosion Equipment Using laboratory testing methods , This equipment accurately simulates the high-temperature, high water-vapor partial-pressure, and high water-vapor-velocity conditions found in turbine-engine operating environments, conducting cyclic tests on materials to evaluate their thermal corrosion and steam-oxidation corrosion, thereby providing a reliable assessment of their thermochemical stability. The system comprises an air-inlet control system, a liquid-inlet control system, a uniform vaporization unit, heated piping, and a heating reactor, among other components. It is primarily suited for applications in high-temperature thermal-barrier coatings, composite materials, alloys, and related fields.

Equipment Characteristics

·Precise control of liquid inflow

·Uniform vaporization of liquid water and gas mixing

·Multiple flow ranges available for the carrier gas: 300ml/1000ml/3000ml (Static)

· Maximum temperature options: 1200℃/1600℃

· Multiple process sets can be preconfigured, with each set 50 Program segment Control