Dry coatings and ecodesign Part. 2-Tribological performances

The goal of this study is to find an industrial alternative application to hard chromium plating. The first part presents the appropriate environmental and chemical behaviour of NiCrBSi alloy and AlSI 316L stainless steel coated by thermal spraying and laser cladding. This paper will concern the wear resistance of these dry coatings. However, stainless steel has awful performance in friction contacts, and this material cannot be suggested as a substitute solution to hard chromium coating for applications where the wear resistance is an important issue. Therefore the tribological pin-on-disc tests will only concern the NiCrBSi coatings. Consequently in the second part, tribological characterizations were carried out in order to determine the alternative potential of NiCrBSi coatings compared to electrolytic hard chromium plating, in applications to resist wear. The coatings are sprayed by Atmospheric Plasma Spraying (APS) and laser cladding (with a diode laser). Especially, the dry coated samples present a good tribological behaviour, whereas the wear mechanisms are different between APS and laser cladding coated samples. Laser cladding allows the manufacture of denser coatings, thus the mechanical properties are increased while the wear rate was reduced. At the same time, APS coated samples show a lower value of shear strength in comparison with laser cladding. That is the reason why fatigue is the main wear mechanism, and this process is called splat delamination. (C) 2009 Elsevier B.V. All rights reserved.