White Etching Cracking—Simulation in Bearing Rig and Bench Tests

Abstract

White etching cracking (WEC) is a contact fatigue bearing failure commonly observed in wind turbine applications. It can lead to fatigue lifetimes more than an order of magnitude shorter than expected lifetimes. Though various mechanical and chemical factors have shown direct or indirect impacts of on WEC failure, the correlations between these factors are yet to be fully understood. The critical intersection among various lubricant- and non-lubricant-related parameters and their influence on hydrogen diffusion and WEC formation are discussed in this article. Experimental results are shown under diverse operating conditions and contact configurations using three test rigs. This study confirms that the mechanical properties of a rolling contact and lubrication parameters alone cannot predict WEC failure. The formation of a tribofilm and accumulation of atomic hydrogen below the contact surface can be essential to explain WEC events. Higher hydrogen concentration in the WEC zone depends on contact area size, the presence of metal-containing additives in lubricants, and higher frictional energy dissipation. Finally, a mechanism of WEC failure has been proposed that intersects the overlap of hydrogen and subsurface shear stress.