Ultrafine grain formation and coating mechanism arising from a blast coating process: A transmission electron microscopy analysis

Conor F. Dunne, Kevin Roche, Arne Janssen, Xiangli Zhong, M. G. Burke, Barry Twomey, Kenneth T. Stanton

    Research output: Contribution to journalArticlepeer-review

    Abstract

    This article examines the substrate/coating interface of a coating deposited onto mild steel and stainless steel substrates using an ambient temperature blast coating technique known as CoBlast. The process uses a coincident stream of an abrasive blast medium and coating medium particles to modify the substrate surface. The hypothesis for the high bond strength is that the abrasive medium roughens the surface while simultaneously disrupting the passivating oxide layer of the substrate, thereby exposing the reactive metal that then reacts with the coating medium. The aim of this study is to provide greater insight into the coating/substrate bonding mechanism by analysing the interface between a hydroxyapatite coating on both mild and stainless steel substrates. The coating adhesion was measured via a tensile test, and bond strengths of approximately 45 MPa were measured. The substrate/coating interface was examined using transmission electron microscopy and selected area diffraction. The analysis of the substrate/coating interface revealed the presence of ultrafine grains in both the coating and substrate at interface associated with deformation at the interface caused by particle impaction during deposition. The chemical reactivity resulting from the creation of these ultrafine grains is proposed to explain the high adhesive strength of CoBlast coatings.

    Original languageEnglish
    Pages (from-to)1271-1278
    Number of pages8
    JournalSurface and Interface Analysis
    Volume49
    Issue number12
    Early online date11 Oct 2017
    DOIs
    Publication statusPublished - 17 Nov 2017

    Keywords

    • coating
    • hydroxyapatite
    • steel
    • transmission electron microscopy
    • ultrafine grain

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