Graphite is a well-known solid lubricant (SL) additive widely used both as a standalone SL and also as additive in lubricating oils, greases, composites, etc. Size of the additive particles especially nano-particles (NPs) is a major attribute to the performance properties of a composite, oil, grease, etc. This paper highlights the influence of graphite particles of four sizes viz. 50 nm, 450 nm, 4 microns and 10 microns incorporated in the grease in identical amount (4 wt. %) on the anti-friction (AF), anti-wear (AW) and extreme-pressure (EP) performance. The results indicated that all sizes proved beneficial for all the selected properties. Higher the size of particles, lower was the improvement in performance. The particles were most effective as anti-friction additive (AFA) followed by anti-wear additive (AWA) and then extreme-pressure additive (EPA). The NPs exhibited highest improvement as AFA (57%), AWA (41%) and EPA (25%). Raman Spectroscopy proved the formation of exfoliated graphitic layer on the worn surface of balls. Furthermore, SEM micrograph with elemental mapping and XPS spectroscopy analysis proved supportive in comprehending the mechanisms responsible for improved tribo-performance.

石墨是一种众所周知的固体润滑剂（SL）添加剂，广泛用作独立的SL和润滑油，油脂，复合材料等的添加剂。添加剂颗粒的尺寸，尤其是纳米颗粒（NPs）是复合材料，油，油脂等的性能。本文重点介绍四种尺寸的石墨颗粒的影响。润滑脂中加入的50 nm，450 nm，4微米和10微米含量相同（4重量％），具有减摩（AF），抗磨（AW）和极压（EP）性能。结果表明，所有尺寸对所有选定的特性均有益。颗粒尺寸越大，性能改善越低。颗粒最有效地用作抗磨添加剂（AFA），其次是抗磨添加剂（AWA），然后是极压添加剂（EPA）。NPs表现出最高的改善，AFA（57％），AWA（41％）和EPA（25％）。拉曼光谱证明在球的磨损表面上形成了脱落的石墨层。此外，具有元素映射的SEM显微照片和XPS光谱分析证明有助于理解导致摩擦性能提高的机理。