RESIDUAL-STRESSES AND CRYSTALLOGRAPHIC TEXTURE IN HARD-CHROMIUM ELECTROPLATED COATINGS

The X-ray diffraction method was used to study the structural and mech anical state of electrodeposited chromium coatings. Experiments were p erformed on layers of various thicknesses, plated on different types o f substrates, and the evolution of the stress state as a function of d epth was studied. The dependence of the texture on the thickness of th e coatings and the substrate material was also studied, The effects of the texture on the values of the X-ray elastic constants (XEC) were t aken into account using the orientation distribution function (ODF) or the crystallites group method. The elastic behaviour of the diffracti ng domains was studied in 3 ways: using the anisotropic self-consisten t Kroner-Eshelby model, assuming Reuss' hypothesis, and considering th e isotropic case. Final values of residual stresses are compared and a simple method of evaluation is proposed. The chromium deposits were p lated by direct current. They are very cracked and exhibit a fibre tex ture with a [111] axis. The residual stresses are tensile with values about 800 MPa at the surface, decreasing with depth according to the t hickness of the layer, and increasing again at the coating-substrate i nterface. (C) 1997 Published by Elsevier Science S.A.