Microstructure and Residual Stress in Shot Peened and Superfinished Gearwheel Teeth

Author:  M. Bandini, M. D’Incau, P. Scardi
Source:  ICSP-13
Doc ID:  2017063
Year of Publication:  2017
Abstract:  
Introduction: Shot peening is acknowledged as one of the most effective treatments to increase fatigue resistance of mechanical components. A jet stream of spherical shots strikes the surface of a metallic component. The surface layers are plastically deformed whilst the underlying ones remain elastic. The main effects are the creation of a compressive residual stress field and a microstructure modification in the surface layers of the material. A side effect is usually an increase of the surface roughness. In automotive field, superfinishing is a well-known mechanical treatment applied in order to reduce surface roughness of gearwheel teeth contact surface. In this field, surface roughness is commonly considered a key factor for lubrication, contact fatigue performance and transmission efficiency. As a rough idea, during superfinishing, workpieces are put in a vibratory tumble in conjunction with abrasive media and soap or chemical accelerant. Superfinishing is commonly considered as not effective on preexisting compressive residual stresses.