Tribology and Lubricants

Korean Tribology Society (한국트라이볼로지학회)
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A Study on the Tribological Characteristics of Low Friction Coating Deposited on SUJ2 Bearing Steel

고탄소크롬 베어링강 2종(SUJ2) 베어링강에 증착된 저마찰 코팅의 트라이볼로지적 특성 연구

  • Kang, Kyung-Mo (Graduate School, Dept. of Mechanical Engineering, Yonsei University) ;
  • Shin, Dong-Gap (Graduate School, Dept. of Mechanical Engineering, Yonsei University) ;
  • Park, Young-Hun (Material Innovation Team, Advanced Material R&D Center, ILJIN Group) ;
  • Kim, Se-Woong (Material Innovation Team, Advanced Material R&D Center, ILJIN Group) ;
  • Kim, Dae-Eun (Graduate School, Dept. of Mechanical Engineering, Yonsei University)
  • 강경모 (연세대학교 대학원 기계공학과) ;
  • 신동갑 (연세대학교 대학원 기계공학과) ;
  • 박영훈 (일진그룹 선행재료연구센터 재료이노베이션팀) ;
  • 김세웅 (일진그룹 선행재료연구센터 재료이노베이션팀) ;
  • 김대은 (연세대학교 대학원 기계공학과)
  • Received : 2018.09.15
  • Accepted : 2018.11.13
  • Published : 2018.12.31
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Abstract

In order to reduce resistance torque and energy loss, minimizing friction between race surface and rolling elements of a bearing is necessary. Recently, to reduce friction in bearing element, solid lubricant coating for the bearing raceway surface has been receiving much attention. Considering the operating conditions of real bearings, verifying the effect of solid lubricant coatings under extreme conditions of high load that is more than 1 GPa is necessary. In this study, we evaluated the friction and wear characteristics of SUJ2 bearing steels deposited by carbon-based coatings (Si-DLC, ta-C), $MoS_2$ and graphite. In case of $MoS_2$ and graphite coatings, different surface treatments were applied to the coatings to verify the effect of surface treatment. A pin-on-disc type tribotester was used to evaluate the tribological characteristics of the coatings. It was possible to quantitatively estimate the friction and wear characteristics of solid lubricant under dry and lubrication conditions. The carbon-based coatings improved the friction and wear properties of SUJ2 bearing steels under the high load condition, but $MoS_2$ and graphite coatings were not suitable for high load conditions due to its low hardness. Different friction and wear behaviors were found for different substrate surface treatment method. Also, it was confirmed that solid lubricant coatings had a more positive effect than just applying the lubricant for improving the tribological characteristics.

Keywords

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Fig. 1. Bare SUJ2 and coated specimens.

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Fig. 1. Bare SUJ2 and coated specimens.

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Fig. 2. Scheme of MoS2, graphite coatings.

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Fig. 2. Scheme of MoS2, graphite coatings.

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Fig. 3. Pin-on-disc rotational type tribotester.

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Fig. 3. Pin-on-disc rotational type tribotester.

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Fig. 4. Nano-indentation of carbon-based coatings.

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Fig. 4. Nano-indentation of carbon-based coatings.

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Fig. 5. Friction coefficient in dry condition.

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Fig. 5. Friction coefficient in dry condition.

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Fig. 6. Lubricated specimen.

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Fig. 6. Lubricated specimen.

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Fig. 7. Friction coefficient in lubricant condition.

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Fig. 7. Friction coefficient in lubricant condition.

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Fig. 8. Cross section images of wear tracks and surface profile curves for (a) Substrate[SUJ2] (b) Si-DLC coating (c) ta-C coating.

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Fig. 8. Cross section images of wear tracks and surface profile curves for (a) Substrate[SUJ2] (b) Si-DLC coating (c) ta-C coating.

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Fig. 9. Cross section photos of wear tracks and surface profile curves for (a) MoS2 coating treated by sand blasting, (b) MoS2 coating treated by manganese phosphate, (c) Graphite coating treated by sand blasting, (d) Graphite coating treated by manganese phosphate.

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Fig. 9. Cross section photos of wear tracks and surface profile curves for (a) MoS2 coating treated by sand blasting, (b) MoS2 coating treated by manganese phosphate, (c) Graphite coating treated by sand blasting, (d) Graphite coating treated by manganese phosphate.

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Fig. 10. Wear rate for various solid lubricant coatings.

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Fig. 10. Wear rate for various solid lubricant coatings.

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Fig. 11. Cross section images of wear tracks for (a) Substrate[ SUJ2], (b) Si-DLC coating, (c) ta-C coating, (d) MoS2 coating treated by sand blasting, (e) Graphite coating treated by sand blasting.

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Fig. 11. Cross section images of wear tracks for (a) Substrate[ SUJ2], (b) Si-DLC coating, (c) ta-C coating, (d) MoS2 coating treated by sand blasting, (e) Graphite coating treated by sand blasting.

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Fig. 12. Wear rate for substrate[SUJ2] and various solid lubricant coatings.

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Fig. 12. Wear rate for substrate[SUJ2] and various solid lubricant coatings.

Table 1. Friction test conditions

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Table 1. Friction test conditions

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Table 2. Vickers hardness and conversed value

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Table 2. Vickers hardness and conversed value

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References

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