Abstract

This study investigates the elemental composition and surface morphology of solid tribochemical films formed on steel surfaces. The reversible addition-fragmentation chain transfer (RAFT) method was used to synthesize nine different metal-free polymers, which were blended into commercial base oils. The polymers were either homopolymers of dodecyl methacrylate and ethylhexyl methacrylate or were co-polymers of these monomers with six polar monomers. After tribological testing at 100 °C using the ball-on-flat geometry, the resulting tribochemical films were imaged using scanning electron microscopy (SEM) and optical microscopy. The resulting tribochemical films have thicknesses around 50–100 nm. Two of the films corresponding to small (P1—imidazole-containing copolymer) and large (P3—less polar homopolymer) wear were cross-sectioned using focused ion beam (FIB) and analyzed for elemental composition using energy-dispersive X-Ray (EDX) mapping. Oxygen and nitrogen enrichment was observed, consistent with the relative chemical composition of the precursor polymers. Transmission electron microscopy (TEM) evidence suggests that at the worn surface, some organic elements penetrate or are mixed into the steel substrate giving an interlocking appearance. The two samples examined with TEM showed that P1 tribofilm is diffused or mixed with the steel substrate more so than P3, suggesting a stronger affinity and contact during tribofilm formation.

Graphic Abstract

中文翻译：

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X射线光谱和光学轮廓分析法研究聚甲基丙烯酸酯摩擦化学薄膜

摘要

这项研究调查了在钢表面形成的固体摩擦化学膜的元素组成和表面形态。可逆加成-断裂链转移（RAFT）方法用于合成九种不同的无金属聚合物，将其掺入商业基础油中。该聚合物是甲基丙烯酸十二烷基酯和甲基丙烯酸乙基己酯的均聚物，或者是这些单体与六种极性单体的共聚物。在100°C下使用球形测球几何学进行的摩擦学测试后，使用扫描电子显微镜（SEM）和光学显微镜对所得的摩擦化学膜成像。所得的摩擦化学膜的厚度约为50–100 nm。分别对应于小（含P1-咪唑的共聚物）和大（P3使用聚焦离子束（FIB）对磨损进行了横截面分析，并使用能量色散X射线（EDX）映射分析了元素组成。观察到氧和氮富集，与前体聚合物的相对化学组成一致。透射电子显微镜（TEM）的证据表明，在磨损的表面上，一些有机元素会渗透或混入钢质基材中，形成互锁的外观。用TEM检查的两个样品显示，P1摩擦膜比P3扩散或混合在钢基底上的程度更大，表明在摩擦膜形成过程中，亲和力和接触性更强。

图形摘要