The Influence of a Class of Surface Defects on the Scuffing Performance of High-Speed Spur Gears

Abstract Gear teeth experience contact conditions that vary continuously as they pass through the meshing zone. As such, surface defect size and position on a gear tooth become relevant to the gear scuffing performance. High-speed gearbox cost and reliability can be balanced by quantifying the impact of surface defects on scuffing behavior. Pursuant to this, representative defects in the form of scratches were applied to the contacting surfaces of high-quality spur gear specimens. These damaged gears along with an undamaged baseline gear pair were tested through a staged scuffing protocol that increased the operating load, speed, and lubricant temperature incrementally. Metrological procedures were developed to quantify scratch parameters and to track surface damage throughout test stages to document the evolution of the defects. It was concluded that (i) larger scratches generally decrease scuffing performance, (ii) the location of scratches on the tooth surface is critical to scuffing performance because low sliding velocity regions were more tolerant to damage, and (iii) increased wear and heat generation were observed at defect locations in high-sliding regions.