All-steel and Si3N4-steel hybrid rolling contact fatigue under contaminated conditions

Ball-on-rod rolling contact fatigue experiments were performed using M50–M50 all-steel and Si3N4–M50 hybrid components, respectively. Experiments were performed using a jet turbine engine lubricant in the as-received condition or with particulate contaminants added. The added particulate contaminants were Arizona test dust or glycothermally synthesized α-Al2O3. Wear performance of the all-steel and hybrid rolling systems was evaluated with and without particulate contaminants in the lubricant. Wear surfaces were analyzed using optical microscopy, scanning electron microscopy, surface profilometry, and atomic force microscopy. Wear mechanisms, volume specific wear rates and modes of failure were determined for all systems. The primary wear mechanism produced in rolling contact fatigue experiments is shown to be contact stress fatigue, with secondary mechanisms of indenting, cutting, plowing and embedding occurring as particulate debris passes through the elastohydrodynamic lubricant layer between the ball and rod surfaces.