The effect of Cr interlayer on the microstructure of CrN coatings on steel

The effect of electroplated Cr interlayer on the microstructure of CrN coat ings on AISI 4140 steel were investigated. Two types of CrN-coated specimen s by cathodic are plasmas were prepared with and without an intermediate la yer deposited by electroplated hard chrome (CrN/steel and CrN/Cr/steel). Th e microstructure and crystallinity of chromium nitride have been investigat ed using X-ray diffraction (XRD), cross-sectional transmission electron mic roscopy (XTEM) and selected area diffraction (SAD). Both CrN/steel and CrN/ Cr/steel coating assemblies exhibit microcolumnar morphologies. However, it is noted that the columnar structure of CrN coating directly on steel is l ess evident, strong, and upward in comparison with that deposited on electr oplated chromium layer. For CrN/Cr/steel assembly, the preferred orientatio ns of CrN(220) and Cr(200) are observed. (C) 2000 Elsevier Science B.V. All rights reserved.