IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Applied Surface Analysis Tuesday Sessions
       Session AS-TuP

Paper AS-TuP10
Structure and Corrosion Properties of PVD CrN Coatings

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Aspects of Applied Surface Analysis II Poster Session
Presenter: A. Matthews, Hull University, UK
Authors: C. Liu, Loughborough University, UK
Q. Bi, Hull University, UK
H. Ziegele, BMW Group, Germany
A. Leyland, Hull University, UK
A. Matthews, Hull University, UK
Correspondent: Click to Email
Corrosion of PVD CrN coated steels in an aqueous solution is usually by galvanic attack due to the difference in electro-potentials between the steel substrate and the coating material which causes corrosion activity in through-coating defects (e.g. pinholes). The structure related variables which can determine corrosion performance of CrN coatings include: (i) Surface discontinuities and uniformity of coverage; (ii) Open and through-coating porosity; (iii) Film density and chemical stability; (iv) Growth stresses and associated strain; (v) Interfacial adhesion and the properties of intermediate layers; (vi) Coating thickness; (vii) Substrate properties (e.g. activity and morphology); (viii) Coating composition. In this study, PVD CrN coatings were prepared with different composition, thickness, and surface roughness by changing the nitrogen flow rate, applying multilayering techniques and changing the substrate finish prior to coating, respectively. It has been found that the microstructure of CrN coatings can vary with the N content in the film, thus their corrosion performance can be affected significantly by nitrogen flow rate during coating preparation. The steel substrate surface finish (i.e. roughness) can affect the uniformity and coverage of PVD coatings, as the grooves and inclusions on the original substrate can raise the susceptibility of the coated systems to crevice corrosion. Increased film thickness can greatly reduce the through-coating porosity; this makes the coatings less permeable in terms of solution penetration, such that the corrosion resistance of the system can be enhanced significantly.