Preperation Of Low Friction And Wear Resistant High-Purity Alumina Ceramic

The high-purity alumina ceramics have a series of superior properties compared with metal materials when they were used as friction wear materials, such as better mechanical properties, wear resistance, high temperature resistance, and corrosion resistance and so on. In this research, high-purity alumina ceramic materials were produced on the background of the ceramic yarn guide and the ceramic motor shaft's applications, and the products'properties came up to the figures which were requested on the project contract. The author analyzed the factors that affected the comprehensive mechanical properties, and discussed the friction and wear mechanisms, then built a relationship of the surface roughness and friction coefficient, and did a systematic research on the factors that influenced friction and wear behaviors. Last, a low friction tribological theory was put forward, called 3GMC (Three Kinds of Grain Microstructure Ceramic).First of all, the research studied that how molding way and molding pressure influenced the mechanical properties, and then it compared the molding effect between dry pressing and isostatic pressing. Secondly, two types of materials which were added in different additives were compared: one type of material was MgO-SiO₂-Al₂O₃ system, the additive that added in the materials would form liquid phase during the sintering; another type of material was ZrO₂ toughened Al₂O₃ system, ZrO₂ and Al₂O₃ would form solid solution under high temperature. Generally speaking, the second type of materials have more excellent comprehensive properties than the first type of materials, the main reason was that ZrO₂ particles reinforced the grain boundaries.In order to recognize the factors that influenced the friction and wear behaviors of the alumina ceramics, the research analyzed the internal causes and external causes. For internal causes, mechanical properties were the dominant factors, and microstructure was also very important; for external causes, load and rotational speed were most important factors.This article studied the friction and wear mechanisms of the two types of materials. For MgO-SiO₂-Al₂O₃ system material, the friction and wear mechanisms were abrasive wear and fatigue wear, for ZrO₂ toughened Al₂O₃ system material, the friction and wear mechanisms were abrasive wear and adhesive wear. And the latter material had better friction and wear behavior. This was contributed by the better mechanical properties, in the process of rubbing, the grains were difficult to pull out, there were only mild wears.A relationship between the surface roughness and the friction coeffient was built. The result proved that smaller surface roughness had lower friction coefficient. At the end of this article, the author brought up a low friction theory that called 3GMC principle. It means that if the microstructure of the material included three kinds of grains, the friction coefficient of the material would be lower.