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Effects of Deep Cryogenic Treatment on the Microstructures and Tribological Properties of Iron Matrix Self-Lubricating Composites

State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China
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Metals 2018, 8(9), 656; https://doi.org/10.3390/met8090656
Received: 4 June 2018 / Revised: 4 August 2018 / Accepted: 14 August 2018 / Published: 22 August 2018
The effects of deep cryogenic treatment on the microstructures and tribological properties of the self-lubricating iron matrix composites are investigated. The self-lubricating composites are deeply cryogenically treated at about −196 °C. The results show that with deep cryogenic treatment, the martensite phase transformation occurred from phase γ to α′, and the fine particle carbides precipitated between martensites with the extension of cryogenic treatment time, measured by X-ray diffractometry (XRD) and scanning electron microscope (SEM). Compared with the as-sintered specimen, the maximum hardness of the specimens processed by cryogenic treatment increases by 172.8% from 253.2 HV to 690.7 HV. The materials with deep cryogenic treatment for 8 h show the best tribological properties, i.e., the average friction coefficient decreases by 75% from 0.36 to 0.09, and the wear coefficient decreases by 63% from 341 to 126 × 10−6 mm3/Nm at 150 N and 8 mm/s. The improvement of the tribological property can be primarily attributed to the martensite phase transformation from γ to α′ and the precipitation of fine particles carbides between the martensites, which increase the hardness and the wear resistance after the cryogenic treatment. View Full-Text
Keywords: self-lubricating composites; cryogenic treatment; phase transitions; tribology; wear mechanism self-lubricating composites; cryogenic treatment; phase transitions; tribology; wear mechanism
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Peng, W.; Sun, K.; Zhang, M.; Chen, J.; Shi, J. Effects of Deep Cryogenic Treatment on the Microstructures and Tribological Properties of Iron Matrix Self-Lubricating Composites. Metals 2018, 8, 656.

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