Abstract
NiCr/hBN self-lubricating composites with hBN solid-lubricant contents of 8%, 9%, 10%, 11%, and 12% (mass fractions) were prepared by powder-metallurgy method. Their tribological properties at room temperature and 600, 700, and 800 °C were studied. SEM and XRD were performed to analyze their wear-surface morphology and abrasive-dust composition. Results indicate that the NiCr/hBN self-lubricating composites have favorable tribological properties at room temperature and 600 °C. The optimum comprehensive friction and wear performance are achieved at 10% hBN, and the main wear mechanism is abrasive wear. At 700 and 800 °C, the friction and wear properties of NiCr/hBN self-lubricating composites obviously decline. The wear surface experiences oxidation and the spinel oxides Cr2O3, NiCr2O4, and CrBO3 are formed. The main wear mechanism becomes combined scratching and glue form of adhesive wear, leading to greatly increased wear rate for the NiCr/hBN sel-lubricating composites.
Highlights
In aero-engines, the high-temperature alloy NiCr is used as the base material of the sealing material between the blade and cartridge receiver because of the alloy’s high-temperature wear resistance, oxidation resistance, and high-temperature mechanical behaviors [1,2,3]
Solid lubricants commonly used in self-lubricating composites generally include graphite, MoS2, CaF2, BF2, and hexagonal boron nitride, where graphite and MoS2 can be used only at
If the Ni-Cr/hexagonal boron nitride (hBN) composite does not undergo oxidation, the mating material lubricating film consists of solid lubricant and metal matrix and its friction coefficient is between 0.25 and 0.46 (Figure 3) at room temperature and 600 ◦ C
Summary
In aero-engines, the high-temperature alloy NiCr is used as the base material of the sealing material between the blade and cartridge receiver because of the alloy’s high-temperature wear resistance, oxidation resistance, and high-temperature mechanical behaviors [1,2,3]. Self-lubricating composite preparation by adding solid lubricant to the NiCr-based alloy has become an important research subject and is extensively studied [4,5]. CaF2 and BaF2 have favorable lubricating properties at high temperatures, but they are generally used under dry-friction conditions [8]. HBN has favorable lubricating properties under dry and wet conditions [9] It has a planar hexagonal net layer crystal structure similar to the hexagonal crystal system structure of graphite. No study has reported on the friction and wear properties of NiCr/hBN composites at high temperatures. HBN solid lubricants were added to study the friction and wear behaviors of NiCr/hBN self-lubricating composites at room temperature (25 ◦ C) and 600, 700, and 800 ◦ C. Our results can provide a theoretical basis for the application of NiCr/hBN composites in the aero-engine industry
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