关键词: 干气密封, 碳化硅, 激光微织构, 摩擦学性能, 磨损机理

Abstract:

The friction and wear on the end face of the dry gas seal ring, which leads to the loss of gas hydrodynamic pressure effect and an increase in leakage, is one of the common failure modes of dry gas seals. Therefore, stringent requirements are put forward for the tribological properties of the end face of dry gas seals. The “hard-on-hard” pairing method represented by silicon carbide (SiC) material is one of the mainstream pairing methods for dry gas seals. However, when SiC is paired in a “hard-on-hard” way under dry friction conditions, severe adhesive wear is likely to occur, often showing characteristics of high friction and high wear, which greatly affects the service life of the SiC seal ring. This paper aims to improve the tribological properties of SiC-SiC pairs through surface texturing. It explores the influence of texture size and areal density on the tribological properties of SiC. Regarding research methods, using laser processing technology, 45° elliptical textures with different sizes and areal densities were fabricated on the surface of SiC ceramics. A SiC ball with a diameter of 6 mm was chosen as the friction counterpart, and tribological performance tests were conducted in a ball-on-disc reciprocating manner. A 3D laser confocal microscope was employed to observe the wear scars and calculate the wear rate. A scanning electron microscope was used to observe the microscopic morphology of the wear scars and to explore the influence laws and mechanisms of texture size and areal density on the tribological properties of SiC. The research results indicate that adhesive wear and brittle spalling of SiC occur on the surface of the base material. In contrast, on the textured surface, adhesive wear mainly occurs between the textures perpendicular to the friction direction. Additionally, as the texture size and areal density increase, the average friction coefficient and wear rate first decrease and then increase. The optimal friction and wear performance is achieved when the equivalent diameter is 80 μm and the areal density is 10%, with the friction coefficient and wear rate decreasing by 15.6% and 41.8% respectively compared to the base material. In summary, textures with a reasonable structural design can serve functions such as accommodating wear debris and reducing the friction area, significantly alleviating three-body wear and adhesive wear, thus positively enhancing the SiC surface's tribological properties. The smaller the texture size, the more textures there are in the wear scar, and the more obvious the scratching effect. As the texture size increases, the number of textures in the wear scar decreases, the scratching effect is alleviated, and the friction coefficient and wear rate decline. However, when the texture size is too large, the counter-face ball may sink into the texture, increasing the acting force, and causing significant fluctuations in the friction coefficient during the running-in stage and an overall increase in the friction coefficient and wear rate. When the areal density of the texture is relatively small, the textured surface approaches that of the base material, and the friction-reducing and wear-resistant effects are weak. A moderate increase in the areal density can reduce adhesive wear and enhance the debris-accommodating effect, resulting in good friction-reducing and wear-resistant effects. However, if the areal density is too large, due to the excessively small friction area and high discontinuity, local stress concentration may occur, and the large number of textures may intensify scratching, causing severe abrasive wear. Only when the texture has appropriate size and surface density can it play its role in accommodating wear debris, reducing contact area, reducing abrasive wear and adhesive wear, and improving the tribological properties of SiC.

Key words: dry gas seal, silicon carbide, laser micro-texture, tribology performance, wear mechanism