Cailiao Baohu (Jul 2022)

Study on the Friction Properties of Cr/DLC and CrN Coatings Before and After High Temperature and High Pressure Treatment

  • GUO Wu-ming, WANG Yu-fei, CAO Wen-tao, LI Zhen-dong, ZHAN Hua, WANG Hai-xin

DOI
https://doi.org/10.16577/j.issn.1001-1560.2022.0185
Journal volume & issue
Vol. 55, no. 7
pp. 66 – 73

Abstract

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For improving the friction properties of GH05 superalloy in high temperature and high pressure water environment, Cr/DLC and CrN coatings were prepared on the alloy surface via ion source assisted unbalanced magnetron sputtering and multi - arc ion plating respectively. FGD autoclave was used to conduct the high temperature and high pressure test of the coatings, and scanning electron microscope (SEM) was used to observe the surfaces and cross - sectional morphologies of the coatings. Moreover, a high temperature UMT tribometer and a step height tester were used to study the friction and wear properties of the coatings, and a nanoindenter was employed to measure the hardness and elastic modulus of the two kinds of coatings before and after high temperature and high pressure test. Results showed that the surface morphology and mechanical properties of the CrN coating after high temperature and high pressure test changed slightly in comparison with that before such test. However, the Cr/DLC coating suffered remarkable oxidation. The coating structure became loose, and the bonding force as well as the hardness of the coating significantly decreased. On the other hand, the high temperature and high pressure test led to an increase of the friction coefficient of Cr/DLC and CrN coatings in both dry and water environments, which might be attributed to the oxidation of the coatings’ surfaces and the deterioration of mechanical properties of the coatings. Compared with the sharp decrease of friction properties for the Cr/DLC coating, CrN coating still maintained good friction and wear properties after high temperature and high pressure test. Especially, the wear rate of CrN coating in water environment was only 1.40 × 10-7 mm3/N·m, which was only 1.60% of that of the Cr/DLC coating under the same test condition (i.e., 8.73× 10-6 mm3/N·m). Overall, the CrN coating could greatly improve the service performance of the superalloy under severe working conditions.

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