Development and characteristics of crack-free chromium coatings produced by electroplating

Abstract

SummaryCrack-free chromium coatings have been proposed for use in gun barrels to increase service life by eliminating the spalling which can occur with conventional hard chromium coatings. In this investigation variables which affect the deposition of crack-free coatings by pulse plating and DC plating with an imposed AC ripple were studied. Microstructures and hardnesses were compared with low contractile (LC) and hard chromium plate. Pulse plated coatings (ca 800–900HV) consisted of an agglomeration of small grains interspersed with pores, the size and number depending on the plating conditions. AC ripple coatings were substantially softer (ca 650HV), and had a columnar herringbone type structure at 15% ripple which changed to a granulated structure at 20%.