Fatigue Behaviour of Scratch Damaged Shot Peened Specimens at Elevated Temperature

Abstract

It is clearly shown that surface condition has a strong effect on fatigue life. 80–90% of total high cycle fatigue life is taken up by crack nucleation/initiation at the surface. Shot peening is a quite successful surface treatment process for extending the service life of a large number of components. The benefit is created by the compressive stress field at the surface and a limited effect of cold work, which has advantages in reducing the likelihood of crack formation, Webster et al. [1]. However shot peening only introduces a very thin layer of compressive residual stress, in the order of hundreds of micrometres. Below the compressive layer near the surface is an elastic region in a tension state to achieve equilibrium and not cold worked, which may have a detrimental effect on fatigue life if a scratch created in the treated surface is bigger than the compressive layer, Burgess et al. [2]. Little information is available about the influence of small scratches on a shot peened surface and how it will affect the fatigue life of a component.