Spalling
How does spalling differ from pitting?
Pitting is a superficial form of fatigue (small, shallow craters), whereas spalling is a deeper, more advanced stage where material flakes off completely, often referred to as 'flaking' or 'peeling' in ISO standards.
Is spalling reversible?
No; it is a progressive, irreversible fatigue phenomenon. Once spalling begins, damage escalates exponentially until the bearing fails.
What ISO failure category does spalling fall under?
It falls under 'Fatigue', specifically categorized as both Subsurface-initiated fatigue and Surface-initiated fatigue.
In reliability engineering and CMMS for rotating assets, spalling is a progressive bearing failure mode involving fracturing and flaking of material from rolling contact surfaces due to surface or subsurface fatigue under repeated loading cycles. It is self-accelerating, with each spall creating stress concentration points that propagate additional cracks, leading to catastrophic asset failure if operation continues.
In shop floor maintenance, spalling is detected via increased vibration signatures (high-frequency impacts), audible grinding noises, and visual inspection of flaked material in lubricant or on bearing surfaces. CMMS systems log it as a 'Fatigue' failure mode (ISO category: Subsurface-initiated or Surface-initiated fatigue) to trigger predictive maintenance alerts before total bearing collapse. Immediate asset shutdown is required to prevent propagation, followed by bearing replacement and analysis of lubrication and contamination levels to prevent recurrence.
Inadequate lubrication: Failure to maintain proper lubricant film thickness leads to metal-to-metal contact and accelerated fatigue spalling.
Contamination control neglect: Allowing dirt, water, or debris into the bearing housing creates micro-cracks that propagate into spalls.
Misalignment/overloading: Operating bearings under excessive loads or misaligned shafts concentrates stress and triggers premature subsurface fatigue.