Processing and properties of electrodeposited layered surface coatings

Andy Horsewell

    Research output: Contribution to journalConference articleResearchpeer-review

    Abstract

    Hard chromium, produced by conventional dir ect curl ent (DC) electrodeposition, cannot be deposited to thicknesses gl enter than about 5 mu m because of the buildup of processing stresses which cause channel cracks in the coating. Much thicker chromium coatings map be produced by depositing a layered structure using alternate DC plating and periodic current reversal (PR). Such layering produces a through thickness stepped gradient in residual stresses. Most importantly a bending moment develops in the coating whenever the substrate is compliant. For thin, compliant substrates, the coating clacks and spalls off early on. For thick, non-compliant coatings, much thicker coatings can be formed. Fracture resistance must be considered in relation to both specimen and loading geometries. Since the inherent bending moment causes a maximum tensile stress at the coating surface, the loading geometry is almost always analogous to bending, and fracture resistance is provided through deviation of the channel crack by weak interfaces, resulting in 'terrace cracking'.
    Original languageEnglish
    JournalMaterials Science and Technology
    Volume14
    Issue number6
    Pages (from-to)549-553
    ISSN0267-0836
    Publication statusPublished - 1998
    EventInvited paper at Layered structural materials, LSM'97, Institute of Materials, Royal Society - London (GB), 28 Nov
    Duration: 1 Jan 1997 → …

    Conference

    ConferenceInvited paper at Layered structural materials, LSM'97, Institute of Materials, Royal Society
    CityLondon (GB), 28 Nov
    Period01/01/1997 → …

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