Purpose

This paper aims to address the influence of diamond-like carbon (DLC) coatings on the frictional power loss of spur gears. It shows potentials for friction and bulk temperature reduction in industrial use. From a scientific point of view, the thermal insulation effect on fluid friction is addressed, which lowers viscosity in the gear contact due to increasing contact temperature.

Design/methodology/approach

Thermal insulation effect is analyzed in detail by means of the heat balance and micro thermal network of thermal elastohydrodynamic lubrication contacts. Preliminary results at a twin-disk test rig are summarized to categorize friction and bulk temperature reduction by DLC coatings. Based on experiments at a gear efficiency test rig, the frictional power losses and bulk temperatures of DLC-coated gears are investigated, whereby load, speed, oil temperature and coatings are varied.

Findings

Experimental investigations at the gear efficiency test rig showed friction and bulk temperature reduction for all operating conditions of DLC-coated gears compared to uncoated gears. This effect was most pronounced for high load and high speed. A reduction of the mean gear coefficient of friction on average 25% and maximum 55% was found. A maximum reduction of bulk temperature of 15% was observed.

Practical implications

DLC-coated gears show a high potential for reducing friction and improving load-carrying capacity. However, the industrial implementation is restrained by the limited durability of coatings on gear flanks. Therefore, a further and overall consideration of key durability factors such as substrate material, pretreatment, coating parameters and gear geometry is necessary.

Originality/value

Thermal insulation effect of DLC coatings was shown by theoretical analyses and experimental investigations at model test rigs. Although trial tests on gears were conducted in literature, this study proves the friction reduction by DLC-coated gears for the first time systematically in terms of various operating conditions and coatings.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0257/

中文翻译：

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涂有DLC的正齿轮–第一部分：降低摩擦

目的

本文旨在解决类金刚石碳（DLC）涂层对正齿轮摩擦功率损耗的影响。它显示了在工业用途中降低摩擦和降低整体温度的潜力。从科学的角度来看，解决了对流体摩擦的隔热作用，由于接触温度的升高，它降低了齿轮接触中的粘度。

设计/方法/方法

通过热弹性流体动力润滑触点的热平衡和微热网络详细分析了隔热效果。总结了在双盘试验机上获得的初步结果，以分类DLC涂层降低的摩擦和整体温度。基于齿轮效率测试台的实验，研究了涂有DLC的齿轮的摩擦功率损耗和整体温度，从而改变了负载，速度，油温和涂层。

发现

在齿轮效率测试台上进行的实验研究表明，与无涂层齿轮相比，涂有DLC涂层的齿轮在所有工作条件下的摩擦力和总体温度都降低了。对于高负载和高速，此效果最为明显。发现平均齿轮摩擦系数降低了平均25％和最大55％。观察到整体温度的最大降低为15％。

实际影响

涂有DLC的齿轮具有减少摩擦和提高承载能力的巨大潜力。然而，工业上的实施受到齿轮侧面上涂层有限的耐久性的限制。因此，有必要对关键耐用性因素（例如基材，预处理，涂层参数和齿轮几何形状）进行进一步的全面考虑。

创意/价值

在模型试验台上的理论分析和实验研究表明了DLC涂层的隔热效果。尽管文献中对齿轮进行了试验测试，但这项研究首次系统地证明了DLC涂层齿轮在各种工作条件和涂层方面的摩擦减小。

同行评审

本文的同行评审历史记录可在以下网址获得：https://publons.com/publon/10.1108/ILT-07-2020-0257/