RESIDUAL STRESS CHARACTERISATION OF GRIT BlASTED STEEL SURFACES

Abstract

With most surface engineering procedures it is necessary to create good initial surface conditions. In the case of thermal spraying processes it is recommended that a rough surface is created to enhance adhesion of the coating, especially when the coating contains ceramics. For optimum mechanical properties, in particular fatigue behaviour, the surface must remain in a compressive stress state. When high velocity oxyfuel spraying is used a compressive residual stress condition is strongly advised in view of the pressure and velocity with which the powder particles reach the substrate. The method of surface preparation employed can strongly affect the resultant compressive stresses. The effects of grit blasting conditions on the resultant residual stress state have been studied. Compressive residual stress in the surface layer increases with grit blasting time. Time, gun-specimen distance, and impingement angle have also been evaluated and show complementary behaviour.