成型方式对氮化硅轴承球性能的影响

The Influence of Molding Methods on the Performance of Silicon Nitride Bearing Balls

摘要: 氮化硅(Si₃N₄)陶瓷轴承球因其优异的力学性能和物理化学稳定性，在高速精密轴承领域具有广阔的应用前景。成型工艺是影响陶瓷球微观结构与力学性能的关键环节。本文分别采用凝胶注模成型和干压成型两种工艺制备Si₃N₄陶瓷轴承球，在相同烧结条件下进行致密化处理，系统对比两种成型方式对烧结体物相组成、显微组织结构、维氏硬度、密度及抗压碎强度的影响规律。结果表明：干压成型有利于促进α-Si₃N₄向β-Si₃N₄的相转变，但易产生“雪花斑”缺陷及异常粗大的β-Si₃N₄晶粒；凝胶注模成型坯体均匀性更佳，烧结后晶粒以球状/点状α-Si₃N₄为主，夹杂少量长柱状β-Si₃N₄，形成自增强韧化结构。凝胶注模成型样品的维氏硬度(>1700 HV)和抗压碎强度均显著高于干压成型样品，且性能数据均一性更好，密度分布更为均匀。凝胶注模成型能够有效减少微观缺陷，获得更均匀的微观结构，显著提升Si₃N₄陶瓷轴承球的力学性能与可靠性，是制备高性能陶瓷轴承球的优选成型工艺。

Abstract: Silicon nitride (Si₃N₄) ceramic bearing balls have broad application prospects in the field of high-speed precision bearings due to their excellent mechanical properties and physicochemical stability. The forming process is a key factor affecting the microstructure and mechanical properties of ceramic balls. In this paper, Si₃N₄ ceramic bearing balls were prepared using two processes: gel-casting and dry pressing. Densification treatment was carried out under the same sintering conditions, and the effects of the two forming methods on the phase composition, microstructure, Vickers hardness, density, and crushing strength of the sintered bodies were systematically compared. The results showed that dry pressing is conducive to promoting the phase transformation from α-Si₃N₄ to β-Si₃N₄, but it tends to produce “snowflake” defects and abnormally coarse β-Si₃N₄ grains. Gel-casting results in a more uniform green body, with the sintered grains mainly being spherical/point-like α-Si₃N₄, interspersed with a small amount of long columnar β-Si₃N₄, forming a self-reinforced and toughened structure. The Vickers hardness (>1700 HV) and crushing strength of the gel-casting samples are significantly higher than those of the dry-pressed samples, and the performance data are more uniform, with a more even density distribution. Gel-casting can effectively reduce microdefects, obtain a more uniform microstructure, and significantly enhance the mechanical properties and reliability of Si₃N₄ ceramic bearing balls, making it the preferred forming process for preparing high-performance ceramic bearing balls.