Crack Propagation in Zirconia MgO-PSZ Ceramic Material

Abstract

The properties of ceramic materials such as elevated hardness, high temperature capability, low coefficient of thermal expansion are of interest for rolling element materials. Widely used ceramic materials in engineering applications are silicon nitride, zirconia and alumina. The paper presents an experimental study of the fatigue life of MgO-PSZ ceramic material in lubricated contact with defined types of cracks. A ceramic angular contact bearing operation was simulated using a four-ball machine. Zirconia balls were artificially damaged with pre-cracks. Ringformed pre-cracks were propagated on the ball surface by a blunt impact load using a tungsten carbide ball under five various impacts. Research of the presented paper shows that fatigue failure under rolling contact loading is markedly sensitive on ringformed pre-cracks made by a different impact energy (drop height). Propagation of surface pre-cracks takes place under a fatigue load. Primary and secondary surface crack propagations are described.

Analysis of Ceramic Elements with Ring-Crack Defects in Lubricated Rolling Contact

“…The upper ball is the silicon nitride test specimen with a pre-existing ring crack (table 2 presents silicon nitride properties). Four-ball machines have been used to examine rolling contact by various researchers [4][5][6][7][8][9].…”

“…The detailed data concerning experimental research, apparatus for production of crack on the ceramic ball surface, test conditions, etc. were presented in the following papers [3,4,10].…”

“…Another surface cracks caused by blunt impact load have also ring shape and are the most common type found on ceramic ball surface. These defects decrease the rolling contact fatigue performance considerably [2][3][4][5][6] so it is important to understand the failure mechanisms caused by such cracks.…”

“…9 presents silicon nitride ball surface view after 3 hours test where large material removal is visible in the ring mouth area. Detailed experimental research, observations and analysis were described in the following papers [3,4,6,10].…”

Hertzian Crack Propagation in Ceramic Rolling Elements

“…Typical ring cracks were produced by a 400 g impact load, dropped from 300 mm (crack P3), 500 mm (crack P4) and 750 mm (crack P5). Detailed information about test conditions was presented in author papers [6,8,9,10,11].…”