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This paper aims to investigate the temperature dependence of transfer film formation and friction coefficients in NAO friction materials with four different abrasive components, ZrO₂, ZrSiO₄, Al₂O₃ and Fe₃O₄.

8.5% SnS₂ was added as a lubricating component to friction materials. Friction tests comprised 100 times of consecutive braking application for each friction material under constant temperature of 300°C, 400°C, 500°C and 600°C. After the friction tests, the friction surfaces of the counterpart disks were examined by scanning electron microscope to access the formation of transfer film.

Coefficients of friction depended on not only friction temperature but also friction history which is related to development of transfer film. The effect of the transfer film formation was to reduce the friction coefficients for most friction materials. Quantities of the transfer film formation varied with friction materials; at low temperature below 400° the transfer film formation was most active in the Fe₃O₄ materials, while at 600° it was the most active in the Al₂O₃ material. The effect of the lubricating component SnS₂ was to suppress the formation of transfer film, thus enhancing friction coefficients.

The enhancement of friction coefficients with addition of small amount of lubricating components such as SnS₂ is expected to open a new approach in developing high performance-brake pads.

Temperature was the controlling parameter in the present test. Under these test modes, transfer film could be fully developed to access the role of the transfer film.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2019-0427/

The purpose of this paper is to investigate surroundings for transfer film formation and removal, the effect of the transfer film formation on friction coefficients, the effect of four different abrasive components, ZrO₂, ZrSiO₄, Al₂O₃ and Fe₃O₄, on transfer film formation and the effect of lubricating component MoS₂ on transfer film formation and friction coefficients.

Two different MoS₂ contents of 5.5 and 8.5 per cent were added to friction materials with no MoS₂ content, which have four different abrasive components, ZrO₂, ZrSiO₄, Al₂O₃, Fe₃O₄. Friction tests composed of three different stages were conducted for those materials, and the friction surfaces of the counterpart disks were examined by scanning electron microscopy (SEM) to access the formation of transfer film at each stage.

For the transfer film formation, high temperature was a prerequisite, but the magnitude of deceleration rate was not important. The effect of the transfer film formation was to reduce the friction coefficients for most friction materials. Friction coefficients of materials which contain lubricating component MoS₂ were higher than those which contain no MoS₂ for most friction materials. The effect of the lubricating component MoS₂ was to suppress the formation of transfer film, thus resulting in increase in friction coefficients.

The transfer film was rather thin, with thickness of 1-2 µm for most friction materials. That hindered the examination of mechanical properties of the transfer film, such as hardness.

This research explained the surroundings for transfer film formation, and its effect on friction coefficients. The research suggests to suppress the formation of transfer film to make friction materials with high friction coefficient, and the lubricating component MoS₂ can be used for the purpose.

Development of high-friction-brake materials conventionally depends on the use of strong abrasive components, which may induce attacking of counterpart disks. The enhancement of friction coefficients with addition of MoS₂ content is expected to open a new prospect in development of high-performance friction materials, which can be applicable to brake pads for racing cars.

The study is in pursuit of the transfer film formation in successive friction stages, which revealed the conditions for transfer film generation and removal. Specimen preparation for SEM observation of cross section of friction surface was painstaking to not damage the developed friction surface. The study revealed the effect of different abrasive components on transfer film formation and the effect of lubrication contents of MoS₂ on transfer film formation and friction coefficients.

China is currently developing and promoting an industrial cluster policy at the government level. By enacting the ‘Opinion on promoting industrial cluster development’, China is supporting the development of industrial clusters. Building an industrial cluster is done by using a single factor but requires many additional factors like regional characteristics, competitiveness factors are also diversified. To evaluate the competitiveness of the Chinese automobile industry cluster, a competitiveness element index should be developed and a competitiveness evaluation method is needed to evaluate the importance of each element. To accomplish this objective, this research applied the analytic hierarchy process (AHP) and focused on the importance of the competitiveness elements.

This research investigated the character is tics regarding cases of clusters and also analyzed the competitiveness of the Changchun automobile cluster located in northeastern China. The purpose of this research is to help Korean enterprises who enter China in the hopes that Korea will emerge as a top automobile production country.