Abstract
Flaking failure of Si3N4 from a pre-indentation was investigated under lubricated ball-on-plate rolling contact. SEM observations were made both on the contact surface and on the longitudinal section along the rolling direction before and after the flaking failure. Multiple semicircular arc cracks were observed on the contact surface before the failure. A growing main crack with branching cracks was observed on the longitudinal section. It was found that the subsurface main crack branches upward and downward at the crack tip, and the upward branching cracks grow faster than the downward branching cracks. The flaking layer was never separated by the upward branching cracks until the main crack grew into a threshold length.
