The process of degradation of ceramic balls made of Si3N4-based materials in hybrid bearings

DOI: 10.62564/M4-DK1802

Dmytro Kustovskyi, Oleksand Vasylchuk, Viktor Bilorusets

V. Bakul Institute for Superhard Materials, Ukraine


The characteristic operating parameters for such equipment, like aviation GTEs, primarily include high speeds of the power shaft rotation and, consequently, high mechanical and thermal loads on the bearings. Ceramic materials, i.e., hybrid bearings, are proposed for the rolling elements in these bearing units. Ensuring the operational safety of bearings of this class, the problem of predicting wear of their components, is extremely relevant. In our work, we investigate the patterns of the degradation process and determine the optimal composition and structure of sintered ceramics for bearing rolling elements. Search for optimal sintering parameters for materials that provide corresponding physico-mechanical properties[1]. Methods for assessing the degradation of investigated materials after operation under specific conditions: Morphometric analysis of wear products. Various types of microscopy and profilometry of damaged surfaces of ceramic balls. Methods for analyzing the operational characteristics of the "in situ" unit[3][4]: Changes in the unit's vibration spectrum[2]. Changes in the spectrum of acoustic emission. Changes in temperature[2]. Resource prediction based on the analysis of obtained data. Various types of ceramics were considered for the study, among which Si3N4-based material proved to be the best. Microscopy and profilometry revealed changes in surface roughness and the formation of characteristic "material tears" and "pits", known as pitting corrosion. This is a specific case of fretting corrosion, which occurs during the cyclic movement of two contacting surfaces. The images show that the pits have a layered shape, torn due to the formation of subsurface cracks. The structure of the materials of worn balls, the surfaces of which are covered with "pits", has a fragmented structure consisting of particles smaller in size than the original powder used for sintering. The research suggests dividing the operational process into stages: I - cyclic loading of ceramic balls of the hybrid friction pair rolling at high temperatures until the initial damage is detected; II - accumulation of damage in the surface layer due to contact fatigue and initiation of subsurface cracks in ceramic balls; III - formation of surface pitting.

Keywords
Si3N4 hybrid bearings degradation

Acknowledgments
Not provided

References
[1] International standard ISO 3290-2 . Second edition 2014-09-01 [2] Tedric A. Harris, Michael N. Kotzalas. Advanced Concepts of Bearing Technology (Rolling Bearing Analysis, FIFTH EDITION). -CRC Press.- 2006. [3]Tedric A. Harris, Michael N. Kotzalas. Essential Concepts of Bearing Technology(Rolling Bearing Analysis, FIFTH EDITION).- CRC Press.- 2006. [4] Ilaria Ghezzia, Eymard W. Houara Kombaa , Davide Tonazzib , Nathalie Bouscharaina , Gwenole Le Jeunec , Jean-Baptiste Coudertc , Francesco Massia/ Damage evolution and contact surfaces analysis of high-loaded oscillating hybrid bearings / Wear 406–407 (2018) 1–1