Barely scratching the engineered surface

Emerging engineered-surface treatments work at the micron scale to boost load capacity of bearings, gears, and other components. Tests on helical gears (case carburized + ground) in automatictransmission fluid at constant pitch-line velocity 7,400 fpm. Contact stresses ranged from 190 to 261 ksi. Baseline gears are ground with in. Technicians boosted torque in steps until they saw scuffing. Treated gears handled up to 70% more torque than untreated. A topographical-modified surface compared to a standard ground surface. Engineered surfaces are flatter and less directional than ground surfaces, which helps reduce microwelding and adhesive wear. Timken ES coatings are about 1 to 3-m m thick and consist of metal carbides in a flexible, diamondlike matrix. Acurrent challenge for automotive engineers is to raise drivetrain loads without upsizing parts. The conventional approach first optimizes gear-tooth geometry, materials, and surface finishes of ground and honed parts. But after exhausting these "macro" techniques you may want to give surface engineering a look before initiating costly redesigns. Timken Engineered Surfaces, for instance, alter the physical or chemical properties of component surfaces at the micron scale. Doing so can improve wear, fatigue, and frictional performance of bearings, hydrostatics, engine components, and gear trains. For example, engineering the surfaces of transmission gear teeth can extend life about threefold. Engineered Surfaces include topographical modification and coatings. Topographical modification brings surface roughness below levels possible by conventional grinding or honing. The proprietary process lowers asperity heights, producing a flatter, nondirectional surface that is less prone to microwelding and adhesive wear than ground surfaces. A typical ground surface has about a 12 to 20m in. finish. Topographical-modified surfaces, for comparison, have 2 to 3m in. surface finishes. Smoother surface finishes also raise the dimensionless quantity, = clearance between parts (in.) and 1,2 are the surface finishes of mating parts (in.). Metal-to-metal