Effects of Spectrum Loading and break in period using molybdenum disulphide (MoS2) and zinc dialkyl dithiophosphate (ZDDP) as EP additives in lithium based grease

IF 1.5 4区工程技术 Q3 ENGINEERING, MECHANICAL Industrial Lubrication and Tribology Pub Date : 2024-04-16 DOI:10.1108/ilt-01-2024-0016

Gabi N. Nehme, Najat G. Nehme

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Abstract

Purpose

The purpose of variable loading conditions (392 N-785N-392N-785N) with break-in period were used to study interactions between zinc dialkyl dithiophosphate (ZDDP) 0.1 P% (phosphorus) and fine-grade molybdenum disulfide (MoS₂) 3%, in different mixtures of NLGI 2 lithium stearate grease. Four-ball wear tests were used to evaluate the tribological properties of different grease mixtures such as coefficient of friction and wear. ASTM 2266 as reported by earlier studies is useful, but it is not representative of real-life applications where variable loads and speeds and different break-in periods play a role and could change the results and the nature of tribofilms.

Design/methodology/approach

In this study, chemical and mechanical properties of tribofilms were examined. Moreover, design of experiment was used to examine the data and shorten experimentation time. Research described here is investigating variable loading conditions for real-life applications by using a break-in period of 2 min at the start to minimize asperities and establish a clean surface. Design expert (DOE) analyzes responses to reveal those variables that are single factor and those that are multifactor whether synergistically or antagonistically.

Findings

The results indicated that spectrum loading with break-in period showed reduction in wear when tested in greases with ZDDP/MoS₂ combinations. Ramping up or down the load every 7.5 min for a rotational speed of 1,200 rpm and a total of 36,000 revolutions or 30-min time slowed the wear properties of lithium-based grease under different MoS₂ and ZDDP concentrations. Experiments indicated that wear was largely dependent on the loading condition and ZDDP additives during specific break-in period at 1,200 rotational speed. It is believed that MoS₂ greases perform better under spectrum loading and under constant loading when mixed with ZDDP phosphorus.

Originality/value

This research indicates that there is a synergistic interaction between ZDDP, MoS₂ and variable loading especially when a break-in period is applied. The results indicated that wear was largely dependent on the specific speed used with spectrum loading as presented in the energy dispersive spectroscopy and the Auger electron spectroscopy analysis, and thus a 3% MoS₂ grease with ZDDP (phosphorus: 0.1 Wt.%) are needed to improve the wear resistance and improve the friction characteristics.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0016/

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在锂基润滑脂中使用二硫化钼（MoS2）和二烷基二硫代磷酸锌（ZDDP）作为极压添加剂对光谱加载和磨合期的影响

目的利用带有磨合期的不同加载条件（392 N-785N-392N-785N）研究 NLGI 2 硬脂酸锂基润滑脂不同混合物中 0.1 P% 的二烷基二硫代磷酸锌（ZDDP）（磷）和 3% 的高级二硫化钼（MoS2）之间的相互作用。四球磨损试验用于评估不同润滑脂混合物的摩擦学特性，如摩擦系数和磨损。早期研究报告中的 ASTM 2266 标准是有用的，但它不能代表实际应用，因为在实际应用中，不同的负载和速度以及不同的磨合期都会发挥作用，并可能改变结果和三联膜的性质。此外，还使用了实验设计来检查数据并缩短实验时间。此处描述的研究是通过在开始时使用 2 分钟的磨合期来调查实际应用中的可变加载条件，以尽量减少毛刺并建立清洁的表面。设计专家（DOE）对反应进行分析，以揭示哪些变量是单因素，哪些变量是多因素，是协同作用还是拮抗作用。研究结果表明，在含 ZDDP/MoS2 组合的润滑脂中进行测试时，带磨合期的频谱加载可减少磨损。在转速为 1,200 rpm、总转数为 36,000 转或 30 分钟的条件下，每 7.5 分钟增加或减少一次负载，减缓了不同 MoS2 和 ZDDP 浓度下锂基润滑脂的磨损特性。实验表明，在转速为 1 200 转/分的特定磨合期内，磨损在很大程度上取决于加载条件和 ZDDP 添加剂。该研究表明，ZDDP、MoS2 和可变负载之间存在协同作用，尤其是在磨合期内。研究结果表明，磨损在很大程度上取决于使用频谱加载时的具体速度，能量色散光谱分析和欧杰电子能谱分析均表明了这一点，因此需要使用含 ZDDP（磷：0.1 Wt.%）的 3% MoS2 润滑脂来提高耐磨性并改善摩擦特性。同行评议本文的同行评议记录可在以下网址查阅：https://publons.com/publon/10.1108/ILT-01-2024-0016/。

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来源期刊

Industrial Lubrication and Tribology 工程技术-工程：机械

CiteScore

3.00

自引率

18.80%

发文量

129

审稿时长

1.9 months

期刊介绍： Industrial Lubrication and Tribology provides a broad coverage of the materials and techniques employed in tribology. It contains a firm technical news element which brings together and promotes best practice in the three disciplines of tribology, which comprise lubrication, wear and friction. ILT also follows the progress of research into advanced lubricants, bearings, seals, gears and related machinery parts, as well as materials selection. A double-blind peer review process involving the editor and other subject experts ensures the content''s validity and relevance.