Elucidation of the Low-Friction Mechanism in Sub-nanosecond Laser-Induced Amorphous Fe–C Layers Formed in Lubricating Oil

IF 3.5 3区工程技术 Q2 ENGINEERING, CHEMICAL

Tribology Letters Pub Date : 2026-03-31 DOI:10.1007/s11249-026-02133-0

Xiaoxu Liu, Masato Yamanaka, Haruka Sasai, Satoru Maegawa, Shingo Ono, Fumihiro Itoigawa

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Abstract

To enable in situ, machining-compatible surface modification, sub-nanosecond laser irradiation in polyalphaolefin (PAO) oil was used to directly form amorphous Fe–C layers on medium-carbon steel. In this study, the structural and tribological characteristics associated with the resulting low-friction behavior are investigated. Laser irradiation in oil enables simultaneous carbon incorporation and liquid-confined ultra-fast quenching, producing a fully amorphous Fe–C-rich layer (~ 150–200 nm). Ball-on-disk tests show sustained low friction (μ ≈ 0.10–0.12) only under sufficiently developed irradiation within an intermediate pulse energy range around 500–650 μJ; lower energies yield fragile/discontinuous layers, whereas excessive energy (1000 μJ) promotes crystallization as the solidification path approaches the TTT nose. AFM lateral-force measurements reveal progressive microscale friction reduction upon repeated sliding, accompanied by indentation evidence of softening limited to the topmost ~ 5 nm. Raman spectroscopy and cross-sectional transmission electron microscopy further demonstrate friction-induced partial structural ordering and carbon enrichment within a thin surface zone (~ 5–10 nm), while the underlying layer remains fully amorphous. These results suggest that the observed low-friction behavior is closely associated with a hierarchical structure combining a load-bearing amorphous Fe–C base layer with a dynamically formed, shear-facilitating surface tribo-layer.

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亚纳秒激光诱导非晶态Fe-C在润滑油中形成低摩擦机理的研究

为了实现与加工兼容的原位表面改性，采用亚纳秒激光辐照聚α -烯烃（PAO）油在中碳钢表面直接形成非晶Fe-C层。在这项研究中，结构和摩擦学特性与由此产生的低摩擦行为进行了调查。激光在油液中辐照可以同时实现碳的掺入和液限超快速淬火，产生完全无定形的富铁-碳层（~ 150 ~ 200 nm）。球盘试验表明，在500 ~ 650 μ j的中间脉冲能量范围内，辐照强度足够大时，摩擦持续低（μ≈0.10 ~ 0.12）；较低的能量产生脆性/不连续层，而过高的能量（1000 μJ）则在凝固路径接近TTT鼻子时促进结晶。AFM横向力测量显示，在重复滑动后，微尺度的摩擦逐渐减少，伴随着最上面~ 5nm的软化压痕证据。拉曼光谱和横截面透射电镜进一步证明了摩擦引起的部分结构有序和碳在薄表面区域（~ 5-10 nm）内富集，而底层仍然完全非晶态。这些结果表明，观察到的低摩擦行为与承载非晶Fe-C基层与动态形成的易于剪切的表面摩擦层的分层结构密切相关。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Tribology Letters 工程技术-工程：化工

CiteScore

5.30

自引率

9.40%

发文量

116

审稿时长

2.5 months

期刊介绍： Tribology Letters is devoted to the development of the science of tribology and its applications, particularly focusing on publishing high-quality papers at the forefront of tribological science and that address the fundamentals of friction, lubrication, wear, or adhesion. The journal facilitates communication and exchange of seminal ideas among thousands of practitioners who are engaged worldwide in the pursuit of tribology-based science and technology.