Hard chromium plating of EDT mill work rolls

Abstract

Hard chromium plating of cold mill work rolls is common practice in order to maintain topography and increase roll service life. The paper details the effect of hard chromium plating on electrical discharge textured (EDT) roll surface topography and surface integrity. Comparative data with corresponding non-chromium plated EDT roll samples are also presented and discussed. Irrespective of the EDT roll surface topography, the coating showed a typical surface hardness in the range HV (0.025)=1100–1300 against approximately 800 HV for the roll base material. The thickness of the hard chromium layers was typically 20–25 μm and cracking of the plated layers was clearly evident as a result of high residual stresses. Measurement of surface residual stress using X-ray diffraction techniques in both the longitudinal and circumferential roll directions indicated highly tensile values between 350 and 700 MPa.