Fatigue strength of chromium coated elements and possibility of its improvement with ball peening

The paper presents the results of the investigation of fatigue strength improvement possibilities making use of ball peening. Made of 41Cr4 steel samples with 25 µm thin chromium coatings were tested. Surface stereometric parametres and fatigue strength limit at oscillatory bending were measured. The correlation between the Sa parametre of the ball-peened surface and fatigue strength limit was proved. It was stated that ball peening of chromium coatings produces advantageous, compressive stress in the surface layer and the oscillatory bending fatigue strength of elements with ball-peened coatings can be improved up to 34%, which almost completely reduces the detrimental chromium plating effects. As a result it was found that ball peening can find its application in restoring fatigue strength impaired by chromium electroplating.