INFLUENCE OF THE PRESENCE OF WHITE LAYERS FORMED DURING GRINDING AND WIRE-ELECTRO-DISCHARGE MACHINING ON PVD TIN COATING ADHESION

White layers can be formed during the surface generation of substrates to be PVD coated. The influence of different manufacturing processes used in industry and especially the influence of the possible presence of a white layer, as a consequence of these techniques, on the final adhesion strength of a PVD coating is not well known, In this paper th e link between the presence of different white layers and the final ad hesion is discussed and it is found that white layers formed during gr inding cause no adhesion problems. This is in contrast to white layers formed on wire-electro-discharge machined surfaces, which are in gene ral thicker and give rise to bad adhesion. First measures are taken to avoid the negative in influence of white layers produced by wire-elec trodischarge machining on the PVD coating adhesion.