New Studies May Help Prevent an Old Problem Shot Peening: an answer to hydrogen embrittlement

Author:  Wandell, James L.
Source:  Metal Improvement Co
Doc ID:  1990119
Year of Publication:  1990
Abstract:  
Historically, shot peening of coiled springs ahs been viewed as an ecomomical means of significantly improving their safe operating stress range. Springs, with wire diameters as small as .005 inch, as well as very large ones made from 3.0 inch diameter rod, have been successfully shot peened to increase their fatigue resistance. Peening is also used on an production basis on leaf springs, Belleville springs, and torsions bars. The peening process is also viewed as a cost effective method of increasing a spring's operating life by five to ten times or more when compared to unpeened springs. The performance and life requirements of automobile engine valbe springs is a typical example. Because of these demands, valve springs have been shot peened for more than 45 years. Today, in addition to giving the end user or customer, a highly engineered reliable spring, many requirement s include the parts to be plated. In most cases, the plating is required for added corrosion lresistance. For some parts, it may be just for cosmetic values. Whatever the reason, the plating process may be the chief cause of hydrogen empbittlement. When this occurs, the springs performance as designed will be greatly curtailed. Controlled shot peening may be a preventative method and solution to hydrogen embrittlement problems.